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r-*
HEALTHY DWELLINGS
DOUGLAS GALTON
r
UonDon
HENRY FROWDE
OZTORD triTIVXBSITT FBB8S WABBHOVSII
7 PATEBS08TXB BOW
OBSERVATIONS
ON
THE CONSTRUCTION
OK
HEALTHY DWELLINGS
NAMELY
HOUSES, HOSPITALS, BARRACKS,
ASYLUMS, ETC.
BY
DOUGLAS GALTON
Late Royal Engineers, C.B., Hon.DX.L., F.R.S., Assoc. Inst. C.E,, Hon. M.I.B.A., M.I.M.E.
F.G.S., F.C.S.f F.R.G.S.y ^c. Formerly Secretary Railway Department Board of Trade ,
Assistant Inspector-General of Fortifications^ Assistant Under Secretary of State
for Wary Director of Ptiblic Works and Buildings, 6fc. &*c.
AT THE CLARENDON PRESS
MSCCCLXXX
[i4// rights reserved"]
\,
/s-^-^c^Z^
PREFACE.
The researches of the physiologist and of the
medical man into the laws which govern the preva-
lence of diseases have enabled them, by the gradual
accumulation of information, to lay down the principles
upon which the healthy construction of houses should
rest. It is the duty of the architect, the builder, the
engineer, and the surveyor to apply these principles,
and their correct application is as essential to the efifi-
cient construction of a dwelling as is the quality or
strength of the materials which are used to build the
dwelling.
The object which the author has in view in this trea-
tise is to present in a condensed form a short resume
of the very scattered information which exists bearing
on the construction of healthy dwellings, whether
houses, hospitals, barracks, asylums, or prisons; this
information was embodied originally in a series of
lectures delivered to the officers of Royal Engineers
in their educational establishment at Brompton Bar-
racks, Chatham. The author has expanded the in-
formation thus collected into this volume, which
contains partly an enunciation of principles, and partly
brief sketches to elucidate the application of these
principles. The field embraced is so vast that it was
b
V fX an d
VI Preface.
beyond the scope of this work to enter into the details
which a complete text book would entail; and those
whose business calls upon them to apply practically
the principles of sanitary construction, must seek the
further information they may need from one or other
of the numerous separate treatises already in existence
on each subject.
There is necessarily little that is new in this work.
It contains much that the author has derived from
personal experience, as well as from the opportu-
nities he has had of becoming acquainted with the
progress of sanitary construction in many European
countries, in the United States of America, and in our
Indian dominions, much also has been collected from
published books ; and he trusts that the several
authors of thes^ books will accept the acknowledge-
ment of their works in this preface, and pardon
him for not having invariably furnished references to
the extracts in the body of the work. The following,
among these works, may be usefully referred to by
those who would pursue the subject further; as well
as by architects, builders, engineers, and surveyors,
who are concerned in the application of details, viz : —
The Reports of the Barrack and Hpspital Improve-
ment Commission, the Reports of the Commission on
Cubic Space in Workhouses, and Pollution of Rivers,
Army Sanitary Commission, Indian^ Sanitary Reports,
Reports of Board of Health, Reports of Privy Council,
Reports of Local Government Board, Dr. Parkes on
Hygiene ; the works of General Morin, M. Tresca^ M.
Joly, Dr. De Chaumpnt, F. Sander (Leipzig), R, Raw-
Preface. vii
linson, Richardson, Baldwin Latham, H umber on Water
Supply, Bailey Denton on Sanitary Engineering,
Dr. Edward Smith's Manuals, Hellyer on Healthy
Houses, Teale's Sanitary Defects, Buchan's Plumbing,
Hood on Warming and Ventilation, Leeds on Venti-
lation (New York), Edwards on Fireplaces, Rankine s
Tables, Balfour Stewart on Heat, Box on Heat, Peclet
sur la chaleur, Symons' Rainfall, Buchan s Meteorology,
Ansted's Geology, Tidy's Chemistry, Hurst's Archi-
tectural Surveyors Handbook, Dr. Angus Smith's
works, also numerous papers on Sanitary science in the
Proceedings of the Royal Society, Chemical Society,
Institutions of Civil and Mechanical Engineers and
Surveyors, Society of Arts, etc., and many others.
b 2
CONTENTS.
CHAPTER I.
PAGE
Preliminary Observations 1
CHAPTER 11.
Conditions which Regulate the Healthiness of a Site . 4
CHAPTER in.
Effect of Soils and Local Conditions on Healthiness of Site 20
CHAPTER IV.
Conditions which Regulate the Healthy Arrangements of
Dwellings on a given Area 30
CHAPTER V.
Purity of Air in an Occupied Building .... 37
CHAPTER VI.
Cubic Space and Floor Space .48
X Contents.
CHAPTER VII.
PAGE
Movement of Air 62
CHAPTER Vni.
Preliminary Considerations upon the Inflow and Removal
OF Air 77
CHAPTER IX.
Simple Ventilation without Warmed Air .... 85
CHAPTER X.
Observations on Warming . 95
CHAPTER XL
Action of Open Fireplaces on Ventilation . . .120
CHAPTER XII.
Ventilation in combination with Warmed Air in Rooms
WHERE Open Fireplaces are not in use . . .136
CHAPTER XIII.
Conditions affecting the Internal Arrangements of Buildings 156
CHAPTER XIV.
Conditions affecting Materials and Details of Construction 180
CHAPTER XV.
Purity of Water 198
CHAPTER XVI.
Removal of Refuse 225
Contents. xi
CHAPTER XVII.
PAGE
Drains in a Dwelling 239
CHAPTER XVIIL
Conditions to be observed in Main Sewerage Works . .256
CHAPTER XIX.
Disposal of Water-carried Sewage 273
CHAPTER XX.
Conclusion 286
^ND£X •..*....•.• £\j L
■» —
» mm
CHAPTER I.
^T^TTT TMTNARY OBSERVATIONS.
he science of the
science of counter-
which arise in the
-lese influences may
at, light, electricity,
il, air, water, food.
conditions of sex,
iperament.
ofession, family, or
tudy of all these,
iisideration of those
conditions un-iw* — isses, in which the
architect and the engineer are ino. . ally concerned.
The statistician and the physiologist supply the data which
enable us to determine what is a healthy condition of life ;
and their researches show that the majority of diseases, and
the greater part of the low health, which prevail in any
country arise from causes which are within man's control.
For instance, epidemic diseases are observed to occur in
very different degrees of intensity at different periods, amongst
groups of population exposed to certain unhealthy conditions.
B
2t
CHAPTER I.
PRELIMINARY OBSERVATIONS.
Hygiene is generally defined as the science of the
preservation of health — that is to say, the science of counter-
acting the influences injurious to health which arise in the
surroundings in which man is placed. These influences may
be classed as: —
1st. Physical ; such as conditions of heat, light, electricity,
sound, &c.
2nd. Chemical ; such as conditions of soil, air, water, food.
3rd. Biological or individual ; such as conditions of sex,
age, inheritance, constitution, temperament.
4th. Social ; such as conditions of profession, family, or
nation.
Hygiene, in its wider sense, includes a study of all these.
The present treatise is limited to a consideration of those
conditions included in the first two classes, in which the
architect and the engineer are more especially concerned.
The statistician and the physiologist supply the data which
enable us to determine what is a healthy condition of life ;
and their researches show that the majority of diseases, and
the greater part of the low health, which prevail in any
country arise from causes which are within man's control.
For instance, epidemic diseases are observed to occur in
very different degrees of intensity at different periods, amongst
groups of population exposed to certain unhealthy conditions.
B
21
2 Preliminary Observations.
Sometimes they take the form of pestilences, and immediately
afterwards, the conditions remaining the same, they subside
and all but disappear, again to renew their ravages at some
future periods.
Whilst we have no knowledge of why these epidemics
break out at one time and not at another, there are certain
well-defined conditions which influence materially, not only
their actual intensity, but also their frequency.
Thus intermittent fever was observed to disappear from
places which formally suffered from it, after drainage of the
soil and improved cultivation.
By cleanliness, fresh air, and diminished crowding, the very
worst forms of pestilential fever, which used to commit ravages
similar to those of the plague, disappeared entirely from
English gaols.
The breathing of foul air contaminated by the breath of
other persons appears to be the special agent which de-
velops consumption, and-diseases of that class.
Consumption and tubercular disease used to be rife in
the British army, because barrack rooms were crowded and
unventilated, and the atmosphere close or foul during the
hours of sleep, when the system is more peculiarly predisposed
to its effects. Out of such an atmosphere, which the men had
been breathing night after night, they were taken and ex-
posed on guard to wet and cold, and the disease soon
developed itself. The cessation of these preventible causes
has led to a great diminution of the disease.
Zymotic diseases, namely — fevers, diarrhoea, cholera,
dysentery, &c., are most intensely active where there is
over-crowding, and the repeated breathing of air already
breathed, such air being further contaminated by moisture
and exhalations from the skin ; equally poisonous are emana-
tions proceeding from animal excretions, or from decaying
vegetable nniatter, together with moisture, the want of drainage,
and a foul state of latrines, urinals, cess-pits, and me^nure
Preliminary Observations, 3
heaps. Moreover, cholera and dysentery are intimately
connected with the condition of the water supply : while
an epidemic prevails, the question whether a given population
shall suffer or escape may almost be predicted from a chemi-
cal analysis of the drinking water.
Hence, the causes of the deteriorated health which He more
especially within the scope of the present work, arise from
poisons in the soil we live on, the air we breathe, or the
water we drink — emanating from decomposition, which is
the result of the previous occupation of the locality by some
form of animal or vegetable life.
When, therefore, the degree of health in a community,
a household, or an individual, falls below the ascertained
standard of good health, it is the duty of every individual
in that community to seek out the removeable causes in
operation which are injurious to health, and to remove
them.
Practical sanitary science is thus embodied in the words,
pure air, pure water — these conditions include a pure subsoil.
Where these exist, the highest d^ree of health of which
the human constitution is capable may be anticipated.
These conditions imply a healthy site, a healthy dwelling,
and the rapid removal from its vicinity of everything that
is liable to putrefy.
Whilst it is for the physiologist and chemist to point
out the prevalence of the poison, it is the function of the
engineer and architect to devise means for obviating its
baneful effects.
B %
CHAPTER 11.
CONDITIONS WHICH REGULATE THE HEALTHINESS
OF A SITE.
The healthiness of a site depends, not only on the position
itself^ but also on what lies around it.
The selection both of the position for, and the form of,
a dwelling must largely depend on the climate ; that is to
say, on temperature, on rainfall, on moisture of soil, on the
nature and prevalence of winds.
The engineer may modify the conditions and temperature
of the soil, and diminish atmospheric damp by drainage ; he
may alter the moisture and temperature of the air by plant-
ing or removing forests; he may produce changes in the
immediate surroundings of a locality; but those general
climatic conditions of a country which are due to position on
the globe and to the vicinity of seas or continents are beyond
the control of an engineer.
I. Temperature of Atmosphere,
In classifying the temperature of a country, it may be
said that when the mean temperature of the locality lies
between the thermal equator and the isothermal line of
80° Fahrenheit, the climate is torrid ; between the isotherm
of 80° and that of 60° the climate is hot ; between the
isotherm of 60° and that of 40® the climate is temperate ;
between the isotherm of 40° and 24° Fahrenheit, the climate
is cold. A greater degree of cold represents a polar climate.
But temperature decreases with the altitude of a district
Healthiness of a Site. 5
above the sea. This decrease is, however, subject to many
variations dependent upon latitude, situation, dampness and
dryness of atmosphere, upon the surroundings of the locality,
whether water^ or forest, or desert, or mountains, and even
upon the season of the year and hour of the day. A general
rule, subject to these variations, has been laid down as follows ;
viz. each 300 feet of height above the sea lowers the tem-
perature about 1° Fahrenheit.
Similarly, in passing from the equator towards the pole,
the mean temperature may be said to be lowered by about
9*^ Fahrenheit for every 10° of latitude. A greater variation
of climate, however, than that due to latitude arises from
other causes ; for instance, the relative proximity of a place
to the ocean, the temperature of which prevents an extreme
degree of cold in countries bordering thereon ; also, the
effect of mountain ranges, which deprive the winds which
pass over them of their moisture, and allow of a more com-
plete radiation of heat from the ground, during the long
winter nights, and thus produce an intense degree of cold.
The position of a site as compared with the level of the
adjacent country affects its temperature. For instance, when
the air in contact with declivities of hills and rising ground
becomes cooled by the ground, the cold air will flow down
the sides of hills into the valleys, displacing the warmer air
and forming as it were pools of cold air. Thus rising ground
is, never exposed to the full intensity of the cold.
It is beyond the scope of this treatise to enter fully into
the subject of climatic conditions and temperature. It may
however be observed, that the death-rate in any locality has
been stated to increase with the increase in the difference of
the mean temperature of January and July of that locality.
One of the principal dangers to health in torrid and hot
climates lies in the fact that heat and moisture especially
favour the decomposition of animal and vegetable matter ;
and these climates are, from this cause, liable to be eminently
6 Conditions which regulate the
unhealthy. A high range of mean temperature is therefore
an important element in tropical and subtropical climates.
In the temperate and cold latitudes the conditions of decom-
position are not so intense ; and where they exist they are
more easily controlled.
2. Temperature of Soil.
Daily changes of temperature do not affect the soil to
a greater depth than three feet, varying with the daily
range of temperature.
The annual variation is dependent on the conductivity
and specific heat of the soil, but it does not penetrate below
40 feet, and below %^ feet it is very small. The mean
temperature of the soil follows slowly the mean temperature
of the air. The highest annual temperature of the trap
rocks at Calton Hill, Edinburgh, at a depth of 24 feet,
takes place about the 4th of January, and the greatest
cold about the 13th of July. At Greenwich, which is on
the tertiary gravels, the highest temperature at a depth
of %^,6 feet occurs on the 30th of November, and the lowest
on the first of June. At a depth of 12.8 feet the highest
temperature occurs on the 25th of September, and the
lowest on the 27th of March. For all practical purposes
the temperature in the soil at a depth of from six to eight
feet, may be said to be practically fixed all the year round,
because it follows so slowly the summer and winter changes
that it never attains summer heat or winter cold.
The temperature of the earth increases with the depth.
This rate of increase of temperature varies in different
geological formations.
In the Paris basin it has been estimated at 1° Fahrenheit
for every 55 feet of depth. In England it has been stated
at 1° for every 54i feet. It is also stated that it varies with
the latitude, being lower in the higher latitudes, and higher
towards the equator.
Healthiness of a Site. 7
The mean rate of increase over the globe may be approxi-
mately assumed at i® Fahrenheit for every 50 feet in depth.
The internal heat exercises, under certain conditions, an
influence over the mean temperature of the surface soil of
a locality.
Where the rainfall is tolerably evenly divided over the
year, the average annual temperature of the soil will be that
of the climate of the locality. But in countries with distinct
wet and dry seasons, the mean temperature of the soil will
not necessarily be the same as that of the mean temperature
of the air. Snow, being a bad conductor, prevents the
passage of the heat from the earth into the air, and thus in
countries where snow lies for some time on the ground, the
mean temperature of the earth exceeds that of the air.
The temperature of water in permanent springs is neces-
sarily derived from the subsoil line of fixed temperature, and,
except in the cases just alluded to, it will not be found to
vary more than i® or a° from the mean temperature of the
locality; therefore the temperature of a permanent spring
may be assumed to afford a certain guide to the mean
temperature of a district.
Thus, in England, the permanent springs range in tem-
perature from 49° to 5 1*', the mean annual temperature being
50°. In India the springs will be found to varj^* in different
parts, according to the temperature of the locality ; in some
instances they attain a temperature of from 70° to 80°.
But whilst the mean temperature of the ground depends on
the climate, soils have a very varying conducting capacity for
heat ; loam, clay and rocks are better conductors than sand,
and by allowing the sun^s heat to pass more rapidly down-
wards, do not become heated to so high a degree.
The conducting capacity of the soil has a very important
bearing upon the comfort, if not upon the health, of those
wiio live upon it.
The following table shows the relative power of soils to
8
Conditions which regulate the
retain heat : sand being the worst conductor, lOO is allotted
to it as the standard : —
Sand, with some lime . . . 100*0
Pure sand 95-6
Light clay 76*9
Gypsum 73-2
Heavy clay 71-11
Clayey earth 68.4
Pure clay 66'7
Fine chalk 6i-8
Humus 490
The great retentive power of the sands is thus evident,
and the comparative coldness of the clays and humus.
Under exposure to the sun's rays, herbage lessens the
absorbing power of the soil, and radiation is more rapid
from it, because a portion of the heat is lost by the evapora-
tion which goes oh from the pores of plants, and the leaves
are rapidly robbed of their heat by the adjacent air.
Changes of temperature take place slowly in trees as
compared with the temperature of the air. Trees acquire
the maximum temperature after sunset, whilst the maximum
temperature of the air occurs between 2 and 3 p.m. Hence
the influence of trees is to make the night warmer and
the days colder ; and the heat is more evenly distributed
over the twenty-four hours in countries covered with vegeta-
tion than in those free from it.
Evaporation goes on slowly under trees ; but the vapour,
not being so liable to be removed by the wind, accumulates
among the trees. Hence, whilst forests diminish evaporation,
they increase humidity, and they keep the summer tempera-
ture lower, and the winter temperature higher than it would
be without them. For these reasons, forests may act in the
same way as a range of hills, to increase rainfall in the
summer by causing condensation in the case of warm moist
winds.
3. Moisture of Soil,
The condition which, more than any other, governs the
healthiness of the soil, is the relation which the ground air,
Healthiness of a Site. 9
or air in the soil, bears to the ground water ; that is to say,
the presence or absence of moisture in the soil.
The moisture in the soil, or ground water, depends upon
the amount and mode of incidence of the rainfall; for, as
a rule, rainfall is the parent of the ground water.
Rain varies greatly, both as regards frequency and rate
of fall. In some places it never rains. The heaviest re-
corded average annual rainfall is said to be 600 inches.
This occurs on the Khasia Hills, which rise abruptly opposite
the Bay of Bengal, and are separated from it by 200 miles
of swamps. As much as 700 inches have fallen in a year.
Five-sixths of the quantity of rain falls in about half the
year; 264 inches have been recorded to have fallen in the
month of August alone, and 30 inches to have fallen in one
period of 24 hours.
The basin of the Indus contains districts where the rain-
fall is sometimes as low as six inches in the year.
In England the average rainfall is 32 inches, but the
average gives a wrong impression of the condition of different
parts of the country.
In the west of Great Britain and Ireland, in the immediate
neighbourhood of hills, the average rainfall is above 75
inches ; and in some localities 150 inches have been observed :
in some years it is even higher. In the east of Great Britain,
from 20 to 28 inches of rain falls. The amount of rainfall
is affected by proximity to the sea, as well as by mountain
ranges and hills, from these latter, and other causes, it varies
materially at places a short distance apart, and therefore
each locality must be considered separately.
The average of a series of years is not what an engineer
must look to. He has to deal with the maximum or mini-
mum. In questions of water supply, the minimum of the
yearly fall is what must influence his calculations. But in
questions of the removal of water, he must look to the
maximum, not of the yearly fall only, but to the greatest
lo Conditions which regulate the
amount which may fall in a limited period. The driest
years test water supply ; the wettest years test works.
In the ^4 hours ended 9 a.m., on the 15th of July, 1875,
there was recorded as having fallen at Newport, 5.33 inches ;
Tintern, 5.31 inches ; Cardiff, 4.7 inches.
There are other instances on record of rain having fallen in
England at the rate of four inches in an hour on a limited area.
In fact the rain in this country occasionally falls as heavily as
in India, but a heavy fall does not last for so long a time.
It has been estimated from observations in this country
that the maximum annual rainfall exceeds by one-third,
and the minimum annual rainfall is less by one-third, than
the mean rainfall of a series of years. It has also been
observed that the average annual rainfall of three consecutive
dry years amounts to 80 per cent, of ,the mean annual rain-
fall of a series of years.
The time of the year at which the rain falls, and the
resulting effects on the air and the soil, is a point of great
sanitary importance.
In dry seasons the re-evaporation is rapid. In India,
rain may fall at such intervals in a dry season as to allow
of entire re-evaporation. In wet seasons water falls on water
and flows off in floods.
Experiments would appear to shew that in this country,
on an average, nearly two-thirds of the mean annual rainfall
goes back at once into the atmosphere as evaporation ; but
these experiments were chiefly made on parts of the country
where the rainfall does not materially vary from the mean
annual rainfall. A further portion evaporates slowly from the
soil, or is absorbed by vegetation. The water which is not
evaporated, or absorbed by vegetation, percolates into the
soil, to flow out in springs, streams, and rivers, to the sea,^
* The Upper Thames basin contains 3676 square miles; the mean daily flow
of water over Teddington Lock during ten years, added to the water pumped
into London by the Water Companies, was nearly 140,000,000 cubic feet; the
Healthiness of a Site. 1 1
whence it again passes into the atmosphere, and returns as
rainfall or as dew. For it is evident that if the humidity of
the atmosphere be assumed to be constant for an average of
years, the evaporation over the whole globe must equal the
rainfall*
The proportion of evaporation and percolation in different
soils varies —
1. With the time of year in which the rain falls.
2. With the quality of the soil, with its capacity for heat,
and with the character and extent of the vegetation
with which it is covered.
In England, on an average of years, the spring is the
driest and the autumn the wettest part of the year. The
driest months are March and April, the two wettest months
are October and November.
The greatest percolation takes place after a wet period,
when the soil becomes saturated. In the summer there is
scarcely any percolation. A series of experiments on per-
colation in England, extending over 14 years, showed that in
five of the years there was no percolation during a continuous
period of seven months; and that in one year only, viz.
i860, did percolation take place every month.
In a series of experiments by Mr. Dickenson, it appeared
that from April to September, 93 per cent, of rainfall was
evaporated, and 7 per cent, absorbed ; whilst from October to
March, 25 per cent, was evaporated and 75 per cent, absorbed.
Great percolation follows the thawing of snow, and the
greatest percolation is due to frequent small falls of snow.
The nature of the soil affects the percolation. Through
sand the percolation is great. The evaporation from sand
in this country has been shown by experiment to be 16
average rainfall in the Upper Thames basin during those years was 29.5 inched
= 690,000,000 cubic feet per diem. The proportion which the water brought down
by the river bore to the rainfall during the period was as i : 4'9 ; but probably
some flowed away underground in the porous strata in which the river is situated.
12
Conditions which regulate the
per cent., and the percolation 84 per cent., whereas with
clay and loam^ the percolation was found to be ^7, and
the evaporation 73 per cent.^
In hot climates the relative power of various soils to retain
heat would alter these proportions ; for instance, the evapora-
tion in such cases would be large from sand if unprotected by
herbage.
The presence or absence of vegetation exercises an im-
portant influence on percolation. When vegetation is rapid,
as in the case of growing crops in the spring, it arrests
percolation ; when the ground is covered with forests, the
moisture is retained nearer the surface.
* The following Table gives the result of various experiments on percolation
through different soils : —
Authority.
Dalton . .
Dickenson
Maurice .
Gasparin .
Rister . .
Greaves ....
Laws & Gilbert . .
Dickenson & Evans
Evans ....
Material.
j Earth
) Surface grass
! Gravelly loam
Surface grass
Earth . . .
Earth . . .
I Impervious subsoil )
Sand, cropped i ' ' '
Mean . .
( Loam, gravel, and sand, turfed
I Sand
f Loam, clay subsoil, built
in 20" deep
. Loam, clay subsoil, built
I in 40" deep
Loam, clay subsoil, built
w in 60" deep . . .
Surface soil at Nash Mills
(SoU .
(Chalk
a
&
H
3 years
8
2
2
22
14
5
5
5
25
20
20
a
o •
Is.
25-0
39-0
20*0
30-0
31-3
26*6
832
368
360
286
310
22-0
360
i .
(4 V
75 -o
57-5
6i-o
8o-o
700
68.7
73-4
i6-8
632
64-0
714
69-0
780
640
Healthiness of a Site. 13
Dr. Ebermeyer found at Salzburg that the percolation was
in May, %^,%"
June, 53.1
July, ^3.4 Vper cent, less through turf than through bare
Aug., 29.1Z earth,
Sept., 7^.7^
and that the difference was least in January.
Ebermeyer's experiments, moreover, showed that in the
summer half year, forest soil is moistest, bare open ground
less moist, turf driest.
Forests retain the moisture, protect the soil, and in moun-
tainous countries retard the flow of torrents. Turf produces
to some extent the same effect.
The power of retention of water in the soil exercised by
the planting of trees was exemplified in the Island of Ascen-
sion. That island formed a convenient point for ships to call
at for obtaining water on their way home from the East
Indies. It was a barren rock, to which formerly the water
had to be conveyed in ships. Some years ago, trees were
planted on the Island. These have thriven, and now the rain
which falls, instead of passing away at once into the atmo-
sphere by evaporation, is retained in a sufficient quantity to
fill tanks with water for the supply of the ships which call
there. The problem of the water supply of some others of
our insular possessions might be solved by similar pro-
ceedings.
On the other hand, all growing vegetation evaporates a
large quantity of water. In order to form i lb. of woody
fibre, a plant evaporates i^oo lbs. of water ; consequently a
country covered with forest evaporates an enormous quantity
of water out of the soil, in order to produce a growth of
timber.
When the rainfall has penetrated from \% inches to % feet
into the ground, the loss from evaporation is comparatively
small ; but it varies with the nature of the soil. In the chalk
14 Conditions which regulate the
formation, water will rise by capillary attraction from the
level at which the chalk is saturated, to a considerable height
above that point; while a bed of sand will be dry at the
height of about a foot above the water standing in it.
So long as there is water sufficiently near the surface of the
soil to keep it moist by attraction, evaporation will continue.
Clay and similarly retentive soils do not give off vapour as
copiously as free open soils; therefore a given quantity of
moisture will occupy a longer period in passing off these soils
than is the case with free soils under similar conditions.
The capacity of soils to retain water varies greatly. Im-
permeable granite or marble will hold about a pint of water
per cubic yard. Pure sand will hold 40 or 50 gallons, or
about 17 per cent, of its weight when dry, and the ordinary
red sandstone rock a 7 gallons per cubic yard, or from 7 to
8 per cent, of its weight when dry. London clay will hold 50
per cent, of its own weight when dry, Oxford clay about
30 per cent. Experiments made by Mr. B. Latham in 1879,
for the Royal Agricultural Society, gave the following per-
centages of water by weight which surface soils selected from
different localities will absorb, viz. open gravel from 9 to 13
per cent. ; gravelly surface-soil 48 per cent. ; light sandy soils
from 23 to ^d per cent. ; loamy soil 43 per cent. ; yellow marl
subsoil %^S) per cent. ; stiff land and clay soils from 43.3 to
57.6 per cent.; sandy and peaty soils from 61.5 to 80 per
cent. ; peat 103 per cent. The conditions of two localities may
thus vary greatly, although there may be an apparent general
similarity in the soils.
Under-draining facilitates the passage of the water from
the surface into the ground ; and a smaller evaporation and
greater percolation takes place in drained lands.
A drained field will consequently have a temperature as
much as 6® or 7° Fahrenheit higher than an adjacent un-
drained field. The cause is obvious. To convert water into
vapour absorbs 960** Fahrenheit of heat from its vicinity;
Healthiness of a Site. 15
thus each cubic foot of water evaporated will lower the tem-
perature of something like 3,000,000 cubic feet of air i^ The
lower the water in the soil, the less the evaporation, and the
warmer the adjacent air.
The discharge of underdrains in a free soil of chalk, gravel,
and sand was found, by Mr. Bailey Denton, to be %\ times as
rapid as that from underdrains in a clay soil ; the drains in
the clay being 25 feet apart ; and those in the free soil placed
at irregular intervals widely apart.
The rate at which a soil allows of the percolation of water
regulates the distance apart at which underdrains should be
placed, for the purpose of lowering the subsoil water in land.
In free soils a single drain will lower the water for a large
area ; in clay soils numerous drains are necessary. The dis-
charge from open soils is more regular than from clay;
although clay soils often give out a large proportion of the
rainfall immediately after it occurs. Barometric pressure
may affect the discharge from drainage outlets ; an increased
discharge has been observed to follow a fall in the barometer
without any fall of rain on the surface.
In a country where the proportions of mean annual rainfall
vary so greatly as they do in Great Britain at comparatively
short distances apart, the areas of heavy rainfall have an
important bearing on water supply. On these areas the rain-
fall is more continuous, and the actual amount evaporated will
therefore be less than in the drier parts of the country.
Hence the proportion to the total rainfall, of rainfall which
can be collected from these areas, will be many times greater
than what could be obtained under the most favourable
circumstances in the drier parts of the country.
4. Aeration of Soil.
The level of water in the subsoil regulates the amount of
ground air.
Air permeates the ground, and occupies every space not
1 6 Conditions which regulate the
filled by solid matter, or by water. Thus, it is the same thing
to build on a dry gravelly soil, where the interstices between
the stones are naturally somewhat large, as to build over a
stratum of air. The air moves in and out of the soil in pro-'
portion to barometric pressure, and with reference to the wind.
If there is much water in the soil, the air carries with it watery
vapours, and is cold, and such a site is called damp.
The fact of this continual free passage of air in and out of
the ground makes it important that, not only should the
ground lived on be free from water, but that it should also
be free from impurities. It would be just as healthy (indeed
probably far healthier) to live over a pigstye than over a site
in which refuse has been buried, or in which sewer water has
penetrated, or over a soil filled with decaying organic matter ;
thus, before building on any ground, its nature should be
carefully examined.
It must, however, be remembered that in proportion as
there is a free movement of air in the soil, so is the process of
decay, and consequently the removal of decaying matter,
more rapid. Louis Cr^teur, in his work * Hygiene in the
Battle Field,' gives his experience in disinfecting the pits
where dead were buried near S^dan. The bodies were buried
in chalk, quarry rubble, sand, argillite, slate, marl, or clay
soils, and the work of disinfection lasted from the beginning
of March till the end of June. In rubble the decay had taken
place fully, but in clay the bodies were surprisingly well kept,
and even after a very long time the features could be identified.
Experiments have demonstrated that there is a considerable
quantity of carbonic acid in the ground : a result frequently
of the decay of organic matter. Water which comes up from
deep springs always contains carbonic acid, but it has been
shown that the ground air frequently contains 50 per cent,
more carbonic acid than the ground water ; it seems, there-
fore, that the latter is supplied with its carbonic acid from the
ground air. Recent experiments in India have demonstrated
Healthiness of a Site. " 1 7
that the carbonic acid in air drawn in a particular locality
from a depth of three feet was one-half that obtained from a
depth of six feet.
These experiments have also shown that there are con-
siderable variations in the amount of carbonic acid present in
the soil of localities in close proximity ; the amount was found
to be doubled in a distance of 50 yards, with apparently
similar soil. The processes going on in the soil at these two
spots must have differed materially; and if such processes
affect health, persons inhabiting a building over one of these
sites would be exposed to different hygienic conditions from
persons living over the other.
These facts show the immense importance which the soil
on which dwellings are placed exercises upon health, espe-
cially in cold or damp weather, when the air in the dwelling
is warmer than the air outside ; for then the upward move-
ment of this warmer air will draw in air to supply its place,
from the ground on which the dwelling stands. This move-
ment would be prevented if the whole surface under the
dwelling were covered with an impervious material. But it is
difficult to find a building material impervious to air.
The following table shows the volume in cubic feet per
hour of air which passed through a square yard of wall sur-
face of equal thicknesses built of the following materials, the
pressure being obtained by a difference of temperature of 72°
Fahrenheit inside, and 40° Fahrenheit outside :
Wall built of Sandstone 4.7 cubic feet.
do. Quarried Limestone 6.5 „ „
do. Brick 7-9 ,, »»
do. Limestone lo.i „ „
do. Mud 144 „ „
Concrete is the most convenient covering to be placed
under a building ; it is not impermeable; the lime in it will
absorb the carbonic acid from the ground air for a certain
time, until it is all converted into carbonate of lime, and
C
1 8 Conditions which regulate the
then its beneficial action would be diminished. Asphalte is
more impermeable than concrete.
The amount of the air drawn from the soil may be checked
by raising the floors above the surface of the ground, and
affording free circulation of air from outside between the
raised floor and the ground. In Burmah, the dwellings are
raised on poles. In Italy and France it is usual to build a
basement on open arches, which are used for wood or other
stores, over which the dwelling is constructed.
So little, however, has the influence of ground air been
appreciated in this country that it is only comparatively
recently that the occupation of cellars with walls abutting on
the soil, as habitations, has been prohibited ; and even within
%o years rooms in the basements of barracks have been used
as barrack-rooms for soldiers. The plan of allowing the earth
to rest against the walls of rooms in basements is still unfor-
tunately common.
These considerations show the importance of forming a
deep open area round a house, and carrying it below the level
of the basement floor ; between the floor and the ground there
should always be ventilation to the outer air. Similarly, a
trench should always be dug round a tent. Apart from the
advantage which this affords for draining off the water, the
sides of the trench enable the atmospheric air to permeate
freely to the ground imjmediately under the tent, especially
when the tent stands on a gravelly soil.
Whilst a permanently low water level (say 15 feet) in the
soil may be termed healthy, and a permanently high water
level (say under 5 feet) may be termed unhealthy, a fluc-
tuating water level is very unhealthy, especially when the
fluctuations are rapid. The unhealthiness mainly shows
itself when the level of the ground water falls.
Fever chiefly occurs in flooded districts when the floods
have receded, and in some of the Indian districts where the
earth surface is covered by water and secluded from the air
Healthiness of a Site. 19
there is no cholera ; but when the water falls and the surface
of the country is drying up cholera reappears. The unhealthi-
ness may be due to the decay of organic matter left by
the receding water; but it must be remembered that under
such a condition of flooding, impure water and filth disappear
for the time ; and when the water falls, the surface and the
water sources are again subject to pollution, and soon become
rife with impurities.
It is for these several reasons that it is desirable to keep
the permanent level of water in the soil, where habitations are
placed, as low as possible ; that is to say, to drain it, so as to
allow the air to have free play in the soil. But where the
ground water cannot be maintained permanently at a low
level, then keep it at an even level.
Thus the presence or absence of moisture determines very
much the degree of healthiness of soils. In any country, that
area over which fogs appear soonest after nigfitfall should be
avoided for camping, and should be drained before building.
The water level of every camping ground should be examined
by digging holes ; but a correct idea can be obtained as to
where water is nearest the surface, from observing where the
vegetation is greenest, where midges prevail in the day time,
and where fogs appear soonest at nightfall.
Apart from its effect on the moisture of the soil, vegetation
has an influence of its own on the healthiness of a site.
Plants in respiration absorb oxygen and throw off carbonic
acid, but the action of the cells in which the green matter
termed chlorophyll is formed, which gives colour to vegeta-
tion, is to absorb carbonic acid and to eliminate oxygen.
This action is due to the sun's rays. Vegetation is thus
beneficial, but when in the vicinity of dwellings it should
always be vigorous, healthy, and green; fallen leaves and
decayed vegetation should be rapidly removed like other
refuse from the vicinity of dwellings.
C %
CHAPTER III.
EFFECT OF SOILS AND LOCAL CONDITIONS ON
HEALTHINESS OF SITE.
Dr. Parke's gives the following table to show the relative
healthiness of various geological formations, based upon their
relative permeability —
Permeability of
water.
Emanations into air.
I.
Primitive rocks, clay state,
millstone grit.
Slight.
None.
II.
Gravel and loose sands, with
permeable subsoils.
Great.
Slight.
in.
Sandstones.
Variable.
Slight.
IV.
Limestones.
Moderate.
V.
Sands, with impermeable
subsoils.
Arrested
by subsoils.
Considerable.
VI.
Clays, marls, alluvial soils.
Slight.
Considerable.
VIL
Marshes, when not peaty.
Slight.
Considerable.
Dr. Parkes states that cholera is unfrequent on granite,
metamorphic, and trap rocks. Granite districts are usually
sparsely peopled and the element of overcrowding as a cause
of disease is absent. And a careful collation of facts shows
that so far as cholera is concerned, the site and the geological
formation have nothing to do with it : it occurs where there
is a population in a filthy condition. And as a rule, local
Effect of Soils and Local Conditions. 21
conditions modify the effect of soil and geological formation.
For instance, granitic and other impermeable formations are
termed healthy because the impurities, instead of passing into
the soil, are carried off rapidly by rainfall ; but if filth is
allowed to accumulate they will be unhealthy.
Thus during the first visitation of cholera, one of the places
which suffered most severely, owing to' its filthy local condi-
tion, was Megavissey, on the granitic formation in Cornwall.
There was much sickness and mortality in 1859-60 at Hong
Kong. The peninsula of Kowloon was selected as a sanato-
rium. It was of granite formation, freely exposed to the
winds; it was reputed to possess every qucllity for health.
Huts were built, and the troops were moved into them.
They suffered severely from fever.
This arose from the disturbance in a tropical climate of
the surface soil impregnated with decaying organic matter.
Until soil of that nature has been opened and oxygenised, it
is in the highest degree deleterious.
Brushwood is a source of danger near camps in a hot
climate, but the immediate result of the removal of brushwood
has been found to cause fever, owing to the disturbance of
decaying organic matter occasioned thereby.
In cold countries, the clayey soils are cold ; and as they
prevent the percolation of rainfall, they are also damp, and
favour the production of rheumatism and catarrhs ; for these
reasons sands are generally the healthier soils in this climate.
Sand or gravel soils are, however, only healthy if kept entirely
free from sewage and decaying organic matter, and from
excess of water. If this is not seen to, then expect typhoid
fever from foul subsoil air and polluted well water. More-
over, sand is easily polluted, because the polluted matter on
the surface percolates freely into sand with the aid of rain
water.
On the other hand, in hot countries, sands are objectionable
from their heat, unless they are covered with grass. They do
22 Efi-'ct of Soils and Local Conditions on
not allow the heat to pass through, but radiate it slowly, and
the air is hot over them day and night.
A clay soil is a cold soil, and the air over it is always '
moister than over dry sand, but a clay soil cannot be easily
polluted by sewage water like sand. In some cases fever has
been observed to stop on passing from gravel to clay.
On the other hand, the Indian experience, in some cases,
has shown that fever death-rates are highest in alluvial clay
soils and water-logged ground ; whilst the general death-rate
was highest on porous wet soils ; and that porous wet soils
possess no advantage in the way of escape from fever if they
be deluged with' water.
Pervious beds, such as sand and gravel interlaced with
impervious beds, such as clay or shale, have the great dis-
advantage of sweating out water at the outcrop ; this is a
frequent cause of fever.
A wet hill slope should always on this account be avoided,
if at all practicable, but if it must be used, then it must be
efficiently drained.
The following instance will explain this. Figure 2
shows the slope of the ground falling towards the plain of
Balaclava.
The formations are rock below and above, traversed by a
belt of clay and shale.
The 79th Highlanders were placed on the clay, and as the
Healthiness of Site. 23
material was soft, their huts were placed on terraces cut out of
the hill side, and were thus embedded in the ground, and the
Fig J
Huts on hill-side at Balaclava.
floors censequently were always damp. There was no roof
ventilation. This regiment had half the men down with fever.
The 42nd Highlanders were placed on the rock, and as it
was hard they did not cut into the rock, but preferred building
their huts on projecting terraces, so that they were quite dry,
and air circulated freely round. This regiment did not suffer
from fever,
Fig. 3. 79th hut
The huts on the clay were subsequently altered (Fig. 3),
so as to allow of a clear circulation of air. Drainage and roof
ventilation were provided, as shown in the sketch, and fever
no longer prevailed.
24 Effect of Soils and Local Conditions on
In connection with this, it should be mentioned that where,
from circumstances, tents and buildings must be placed on the
side of a hill, a plateau should be formed to receive them, and
a broad space be left between the hill and the tents or build-
ings. A trench should also be cut to carry off the moisture
between the tent and plateau, and no accumulation of refuse
should be allowed between the hill and the tent or building.
Although the general features of a site may be unhealthy,
when it is absolutely necessary for any reasons, military,
political, or otherwise, that it should be occupied, much
may be done to remedy its unhealthiness.
For instance, if temporary occupation only is contemplated,
probably cutting off the water which may flow from higher
levels, or the adoption of measures already mentioned, such as
digging trenches round tents or huts, would be all that could
be done : but if the ground is to be permanently occupied,
not only the area to be built on, but an area extending to
probably lOO yards round it on every side should be
thoroughly under-drained, and the mouths of the drains
so arranged as to allow the aeration of the soil^ as well as
the removal of the subsoil water. Dwellings should be raised
above the level of the ground, and provided with ventilated
air spaces underneath.
5. Effect of the Conditions of the Adjacent Districts
on Healthiness of a Site.
Elevated positions are generally healthy, but when these
positions are exposed to wind blowing over marshes or mala-
rial ground, their very elevation is a source of danger.
In order to provide a healthy station at Jamaica, an ele-
vated site from 3,500 to 4,000 feet above the sea level, at a
place called New Castle, was selected for barracks. It was
situated on the crest of a spur of land falling rapidly from the
Healthiness of Site. 25
Blue Mountains southwards towards the deep damp valleys
and ravines, filled with tropical vegetation, which connect the
range with the lower country. The sides of the ridge sloped
down at angles of 40° and 50°. The surface was clay mixed
with vegetable matter. The ridge was so narrow that the huts
were placed on terraces cut out of the slopes of the hill,
with but a few feet of space between the back of the hut and
the soil supporting the terrace above. Even in temperate
climates such a position contributes to fever. The result was
that in the yellow fever epidemics in 1856 and 1867, those
huts which were so placed that the malaria blowing up the
valleys must necessarily strike them, yielded a large per-
centage of yellow fever even at this high elevation.
Algeria perhaps offers some of the best illustrations of the
manner in which engineering operations have remedied the
evils of the proximity of marshes.
Bond stands on a hill overlooking the sea; a plain of a
deep rich vegetable soil extends southward from it, but little
raised above the sea level. The plain receives not only the
rainfall which falls on its surface, but the water from adjacent
mountains, and is consequently saturated with wet. The
population living on it and near it suffered intensely from
fever; entire regiments were destroyed by death and in-
efficiency. It was at last determined to drain the plain.
The result of this work was an immediate reduction of the
sick and death-rate.
Such instances might be multiplied.
Irrigation, if applied in excess, is unhealthy, and should
not be allowed near habitations. In Northern Italy irrigated
rice grounds are not allowed within 1000 yards of small
towns, and are required to be placed further from large cities ;
but in these the water is allowed to stagnate in the subsoil.
Where the water is not allowed to stagnate irrigation may be
carried on with less danger.
Fondouc, in Algeria, is situated on sloping ground, imme-
26 Effect of Soils and Local Conditions on
diately above the marshy plain of the Mitidja, and has
mountain ranges behind it. It was first occupied in 1844,
and in the succeeding year half the population was swept
away by fevers and dysentery. During the first %o years the
mortality was 10 per cent. The surrounding marsh has been
cultivated, and there are now upwards of 10 square miles
round the town under cultivation, producing cereals, cotton,
tobacco, and wine.
The cultivation consists of ploughing and trenching com-
bined with irrigation, so that water in excess is not applied.
The mortality now is only 20 per 1000.
In India, wherever water is applied in excess for irrigation,
so as to become stagnated in the subsoil, ague, spleen dis-
ease and fever prevail.
But it is possible to improve such localities by draining
away the superfluous stagnant subsoil water.
In the northern Doab districts in the North-West Provinces
a great diminution of the excessive fever mortality for which
these districts were noted has followed the extension of drain-
age works, by which the water which formerly stagnated on
and in the land is now led away by continuously flowing
streams.
But it is not sufficient to make the drains. All drainage
cuts are liable to become injured, if open, by vegetation, and
in all cases by decay, by atmospheric causes and other means.
If not properly maintained and cleared out, the evils they are
created to remove will recur.
For instance, at Bond, from which, as already mentioned, in
consequence of drainage works the fever disappeared.
The drains were left to atmospheric influences ; they be-
came partially obstructed and irregular, and did not allow the
water to reach the outfall ; the result was a violent outbreak
of fever at Bond attended with great loss of life both civil and
military, an enquiry took place, the drainage was rectified,
and since then Bond has been healthy.
Healthiness of Site. 27
. The engineer thus has it in his hands to mitigate the evils
of a marshy district by providing for the removal of stagnant
water, and to prevent the evils which arise from irrigation by
combining drainage with works intended for irrigation.
6. Summary of Conclusions as to a Healthy Site.
The following is a brief summary of the conclusions to
which the considerations above adduced point —
1. Clay soils should, if possible, be avoided.
2. Ground at the foot of a slope, or in deep valleys, which
receives drainage from higher levels, should be avoided. It
predisposes its occupants, even in temperate climates, to
epidemic diseases.
3. High positions exposed to winds blowing over low
marshy ground, although miles away, are in certain climates
unsafe, on account of fevers. Indeed, it sometimes happens
that a site in the immediate vicinity of a marsh, or other local
cause of disease, especially if protected by a screen of wood,
is safer than an elevated and distant position to leeward.
4. Elevated sites situated on the margin or at the heads of
steep ravines, up which malaria may be carried by air currents
flowing upwards from the low country, are apt to become
unhealthy at particular seasons. Such ravines, moreover,
from want of care, are often made receptacles for decaying
matter and filth, and become dangerous nuisances. In
tropical climates these ravines convey malaria, and occasion
aggravated remittent, or even yellow fevers, at an elevation
which would be otherwise exempt from the action of tropical
malaria.
5. Ground covered with rank vegetation, especially in
tropical climates, is unhealthy, partly on account of the
afnount of decaying rnatter in the soil, partly because the
presence of such vegetation is in itself a mark of the presence
of subsoil water. Or of a humid atmosphere.
28 Effect of Soils and Local Conditions on
6. In warm climates, muddy sea be,aches, or river banks, or
muddy ground generally, if it be subject to periodical flood-
ing, and marsh land, especially if it be partly covered with
mixed salt and fresh water, are peculiarly hazardous to
health.
7. A porous subsoil, not encumbered with vegetaflon, with
a good fall for drainage, not receiving or retaining the water
from any higher ground, and the prevailing winds blowing
over no marshy or unwholesome ground, will, as a general
rule, afford the greatest amount of protection from disease
which the climate admits of.
8. To test the healthiness of a site an enquiry into the rate
of sickness and mortality in the district will afford valuable
information. But care should be taken not to be guided by
the mortality alone. The nature of the diseases, and the facility,
or otherwise, with which convalescences and recoveries take
place, must also be taken into account.
To sum up these conclusions for this country for a site
tQ be selected for occupation. The local climate should be
healthy ; the soil should be dry and porous ; it should be
protected from the north and east by shelter at a sufficient
distance to prevent stagnation of air or damp, — otherwise
the shelter from cold and unhealthy winds, which is an evil
recurring only at intervals, will be purchased by loss of
healthiness at other times. The ground should fall in all
directions, to facilitate drainage ; it should not be on a steep
slope, for high ground rising near a building stagnates the air
just as a wall stagnates it : the natural drainage outlets
should be sufficient and available. There should be nothing
to prevent a perfectly free circulation of air over the district ;
there should be no nuisances, damp ravines, muddy creeks or
ditches, undrained or marshy ground close to the site, or in
such a position that the prevailing winds would blow the
effluvia over it.
The site should, moreover, be thoroughly under-drained,
Healthiness of Site. 29
except possibly in a case where the ground is so elevated and
porous as to ensure that water never remains in it ; and if
there is higher ground adjacent, the water from the higher
ground should be carefully cut off by underground catch-
water drains, and led away from the vicinity of the site.
The object to be attained in laying out the ground is the
rapid and effectual removal of all water from the buildings
themselves, and from the ground in their vicinity, so that
there shall be no stagnation in or near the site.
It is no doubt impossible always to procure a perfect site
for building ; but it will be necessary in the construction of
buildings upon a given site to discount any departure from
these qualifications by additional sanitary precautions in the
building — i. e. by increased expenditure.
CHAPTER IV.
CONDITIONS WHICH REGULATE THE HEALTHY
ARRANGEMENTS OF DWELLINGS ON
A GIVEN AREA.
However healthy a site may be, evil may accrue from the
undue crowding of buildings upon it.
The deteriorating effect of residence in towns has been
frequently noticed. The Registrar-General has shown that a
population of 12,89^,98^^ persons living on 3,183,965 acres in
the districts comprising the chief towns of England, showed
an average death-rate for ten years of 34.4 per 1000 ; whilst
a population of 9,819,^84 living on 34,135,^56 acres in
districts comprising small towns and country parishes, showed
an average death-rate for a similar period of 19.4 per 1000.
Dr. Morgan's paper on the deterioration of races in great
cities shows that of the adult population of London 53 per
cent., of that of Birmingham 49 per cent., of that of Man-
chester 50 per cent., and of that of Liverpool 6% per cent.,
were immigrants from the country settled in the town, and
that the majority of the incomers were men and women in
the prime of life.
The mortality in these four towns averaged 26 per 1000
against 19 per 1000 in the adjacent country districts; the
mortality of persons under the age of 15 being 40.7 per 1000
in these towns against 22, per 1000 in the country districts.
The marriages in the city population were four times as
numerous as in the agricultural counties, but the births in the
Arrangements of Divellings on a Given Area, 31
town population only exceeded those in the agricultural
population by one-sixth.
A statistical analysis by Mr. Francis Galton of the details
of 1000 town families and 1000 country families, selected
from the town of Coventry and the adjacent agricultural
population, showed that the town population supplied to
the next generation only three-quarters of the number of
adults supplied by the equally numerous country population ;
and that in two generations the adult grandchildren of artisan
townsfolk were little more than half as numerous as those of
labouring people who lived in healthy country districts. In
large, closely-built centres of population the ratio would
probably be considerably increased against the town
population.
The greater unhealthiness of towns is largely due to the
too close proximity of the dwellings, the consequent absence
of fresh air, and the saturation of the subsoil with impurities
passing into it from the closely occupied surface.
The subsoil of all large Indian cities has been saturated
with the filth of generations, just as the subsoil of large cities
in ancient times had been saturated.
From this saturation these ancient cities became foci of
disease, and were abandoned.
Many large cities in India contain saltpetre factories, the
nitrogen being derived from the previous contamination of
the soil with decaying animal matter.
The careful paving of a town area, coupled with adequate
drainage to carry off the water falling on the gravel surface,
is a great protection to health.
It is essential for health that buildings should have free
circulation of air all round them, and as much sunlight as
possible.
Rows of back-to-back dwellings which do not admit of
thorough ventilation should not be permitted ; there should
be a clear space sufficient for a free circulation of air at the
32 Conditions which regulate the Healthy
back of every dwelling house, from the level of the lowest
floor or basement, and along its whole width between it and
the building behind it.
In temperate and cold climates buildings should, if possible,
be arranged so as to allow the sun to shine on both of the
principal sides of the building during the course of the day.
Indeed in the general arrangement of buildings or tents or
huts, it may be laid down as a safe rule that the larger the
space that is allowed between them for circulation of air the
more healthy will the occupants be. Hence, if for any reason
it be necessary to lodge a large number of persons on a given
limited area, it is preferable for health to place them in
buildings of several storeys high, designed to afford free
thorough ventilation, and so distributed on the site as to
admit of free circulation of air all round each building, rather
than in dwellings of lesser height which must be in close
proximity, not admitting of free circulation of air.
The following are examples of the death-rates in some of
the most densely peopled districts in the metropolis, as com-
pared with less dense localities.
St. Anne's, Soho ....
Strand .
Brompton
Lewisham
Eltham
Metropolis
Model Lodging Houses, viz. ,
Industrial Lodgings Company*
Metropolitan Association , .
* Registrar's District, Strand.
' „ „ Kensington.
* Lewisham.
Approximate
Number of
inhabitants
per acre.
331-35
241.05
41.05
3-05
1.04
43;
860
1 140
Number of
Houses
per acre.
25.24
22.2^
5.81
0.56
0.18
5-55
Death-
rate.
24.16^
22.42
18.83
22.3
16
18
* The population per acre in one of the buildings of this Company is 2,200.
Arrangements of Dwellings on a Given Area. 33
The examples drawn from towns are from places where
paving and draining have been more or less carried out, and
where, nevertheless, the influence of surface overcrowding on
health is obvious on a comparison being made with less
crowded districts.
The superior healthiness of the Model Lodging Houses is
due partly to the careful provision of sanitary arrangements,
but mainly to the fact that the numerous storeys in these
buildings, whilst affording accommodation for a dense popula-
tion on a limited area, are provided with free through venti-
lation ; in addition to this, ample space is provided all round
the structure for the circulation of air, and impurities are not
allowed to be retained on the open area round the buildings.
With armies, a camp is formed of a number of tents or
huts with circulation of air all round each. But if the force
be large, a too close proximity of tents may be, and certainly
has been, a common cause of camp diseases. A camp is a
temporary town, without paving or proper drainage. It is
only by paving and drainage that the deleterious influence of
surface overcrowding in towns can be reduced to a minimum.
But paving and drainage cannot be carried out to a sufficient
extent in camps to enable the surface to be crowded with
safety to health ; and therefore in laying out a camp the
extent of space allotted to it should be as large as the
nature of the ground, or of the service, will admit ; great care
should be exercised in the selection of places for the deposit
of refuse, and after a temporary camp has been occupied for
some time, the site should be abandoned for a new one.
The Quartermaster-General's instructions for camping,
issued at the commencement of the Crimean War, authorised
densities of population on the camp surface equal to 54^ and
1037 inhabitants per acre. The lowest of these densities is
nearly double that of St. Anne's, Soho, one of the most
densely populated districts in England, where the population
occupies houses of ordinary construction. It includes jiot
D
34 Conditions which regulate the Healthy
only the ground actually covered by tents, but all the open
spaces in the camp. The ground actually covered by tents in
these plans of encampment gave a density of population equal
to 1632^ per acre, or a space of little over 5x5 feet for each
individual.
A comparison of these authorised densities for camps,
which had neither drainage nor paving, with the dense
populations in towns already mentioned, affords an index of
what would be likely to be the influence on health of surface
overcrowding in the camps.
The surface area per tent for different densities of popula-
tion per square mile is as follows : —
Square yards per tent.
Tents per acre.
4
Troops per acre, assuming
1 2 men per tent.
50
100
400
1000
96.6
48.4
4.84
1159-^
580.8
58.
The number of troops to be placed on a given area must
be determined by local circumstances, but the above table
will be useful in enabling a correct judgment to be formed
upon one very important element in the sanitary state of
camps — namely, density of population.
The manner of arranging tents is of importance to health,
as well as to cleanliness.
Battalion tents should never be arranged in double line ;
short single lines are best. The tents in line should be
separated from each other by a space at the very least equal
to a diameter and a half of a tent, and the farther the lines
can be conveniently placed from each other the better.
These are all matters which are necessarily more or less
subject to military considerations, and therefore the object
in pointing them out is to furnish a sanitary standard at
which to aim, rather than to suggest an absolute rule.
Arrangements of Dwellings on a Given Area. 35
The construction of permanent buildings is a matter
over which the architect and the engineer have a more
complete control than over the location and arrangement
of a camp.
The general locality of houses, hospitals, asylums, prisons,
or barracks, and even towns, is no doubt settled by the special
circumstances of each case ; or, in the case of government
buildings, by military or political considerations ; but the
actual site within such general locality, and the arrangement
of buildings on the site, is a matter which falls more imme-
diately within the province of the architect or engineer to
determine.
The health of any building is dependent upon free-moving
pure air, outside and inside its walls ; anything which interferes
with this first condition of health is injurious.
If the building is placed in a town, the health of the
inmates is governed by the same conditions as those of
the rest of the population of the town.
Thus certain barracks in manufacturing towns recently
showed a death-rate of io«88 per 1000, as compared with
a death-rate of 6«98 per 1000 at Aldershot. But there is
some ground for fearing that the continued occupation of
Aldershot as a camp, on a porous soil, without paving or
adequate drainage round the huts, is leading to a gradual
deterioration of the health of the camp.
Where commercial, political, military, or other necessities
require that a building containing a large number of inmates
should be placed in a town, additional precautions must
be taken to render it as little unhealthy as possible.
The enclosure should be sufficient to allow of ample space
being reserved for a supply of fresh air between the enclosure
wall and the inhabited buildings, and between the buildings
themselves.
The sources of impure air within the enclosure, such as
ash-pits, manure-pits, &c., should be reduced to a mini-
D %
36 Healthy Arrangements of Dwellings, &c,
mum, and so placed that the air in their vicinity shall not
stagnate.
In the design of any building intended for habitation the
first consideration is, how can the ground at the disposal
of the architect or engineer be best utilised, so as to
secure pure flowing air and sunlight over every part of the
building.
CHAPTER V.
PURITY OF AIR IN AN OCCUPIED BUILDING.
Having explained the conditions which govern the purity
of the outer air, it is in the next place necessary to consider
what is the accepted meaning of purity of air in an inhabited
building.
In order to appreciate the enormous difference between the
purity of air out of doors and the purity of air in a confined
space, it is necessary to consider what are the constituents of
the outer air.
Standard of Purity in Air.
Air taken under the most favourable circumstances, in free
open spaces or on elevated ground, consists of the following
constituents (Angus Smith) : —
I Oxygen, 1^09 \,o %\\ parts ; izo9*6 mean.
1000 parts \ „
I Nitrogen, 789 to 791 parts.
Moreover, every analysis of air shows the presence in
varying proportions of carbonic acid, vapour of water, organic
matter, ammonia, suspended matter.
The purity or impurity of the air, and its effect on health,
depends upon the greater or less degree in which these
various subsidiary matters are present in the air.
The most important of the gaseous impurities in air which
have an influence on health is carbonic acid COg. It is,
however, less important on account of its own special action,
than because of its use as a measure of the purity of the air.
38 Purity of Air in
. The average amount of CO2 has been taken at 0-400
volumes per 1000 in normal air, although it is not unfre-
quently as low as -a, and sometimes as high as -5, or more.
M. Reiset obtained from a year's observation, at a station
in the country far from dwellings, and situated at about
four miles from Dieppe, an average of •2942 per 1000. The air
above a crop of red trefoil in the month of June gave 'izSgS ;
and at a height of one foot from the soil, in a barley-field
in July, '2829, per 1000 : the corresponding amounts at the
country station being •2915 and •3933 per 1000 respectively.
The presence of 300 sheep near the apparatus raised the
proportion to •3178 per 1000, and at Paris in May 1873-75-79
the mean amount was '3027 per 1000.
The presence of from i«5 to 2 per cent, of this gas pro-
duces in many persons severe headache ; but as much as
3 per cent., or even more, has been found just endurable
under certain circumstances. A candle will be extinguished
with 2'5 per cent. ; and it may be assumed that the presence
of 5 per cent, or over will cause death.
In this connection, it may be mentioned that carbonic
oxyde COj is eminently poisonous. Less than 0*5 per cent,
has produced poisonous symptoms, and i per cent, rapidly
produces fatal results. This gas is formed by the imperfect
combustion of carbon.
The deleterious action of gases disengaged from marshes
has been attributed to the presence of sulphuretted hydrogen,
but the action of these gases is not very accurately
determined.
There are, moreover, various suspended matters in air
which produce disease from mechanical causes, such as the
dust which in Egypt produces a sort of ophthalmia. Bron-
chitis and lung disease prevail in many factories, arising from
the inhalations by the workmen of the dust of coal, sand, and
steel, or of particles of cotton or hemp. Stone masons suffer
from inhalation of stone-dust.
an Occupied Building. 39
The Guards suffered largely about 18 years ago from lung
disease ; one of the contributing causes was assumed to be
the quantity of pipeclay they inhaled in the process of
cleaning their white cloth fatigue jackets.
House-painters suffer from the dust of white lead ; though
in this, as in many cases, the persons suffer as much from
swallowing particles, in consequence of not washing off the dirt
. from their hands before eating, as from breathing the dust.
Of all the impurities of air, that which stands highest in
the scale of injury to health is organic matter. An undue
proportion of carbonic acid may indeed kill outright, but to
the presence of organic matter diseases of impure air are
mainly traceable.
Malaria appears to arise from the poison of decaying moist
vegetable matter in marshes and forests. Typhoid fever is
traceable to the poisonous air which arises from the putrefy-
ing substances in sewers. In camps men have had typhoid
fever in consequence of their tents being placed near to
manure heaps, or on damp soil. Phthisis and other diseases
may result from breathing air rendered impure by the putre-
fying organic matter thrown off from the human body in
the process of breathing and transpiring.
So long as air is in movement out of doors, the products
of vegetable and animal waste are being continually removed
from the air by oxidation. They are also washed out by
rain, or removed by snow and hail. Much of the oxidation
is probably due to the action of ozone, and would not be
^ effected by ordinary or inactive oxygen.
Ozone is oxygen in an altered or allotropic condition, and
appears to be formed by the passage of the electric spark
through dry oxygen or by slow oxidation of phosphorus and
other essential oils in presence of moisture. Ozone is
insoluble in water.
Ozone is rarely, if ever, absent in fine weather from the air
of the country ; but it is more abundant, on the whole, in the
40 Purity of Air in
air of the mountain than of the plain. It is also said to occur
in larger quantity near to the sea than in inland districts. It
has been found to an unusual amount after thunderstorms.
There is great variety of opinion as to the conditions which
produce ozone. According to some observers, the amount of
ozone in the air is greater in winter than in summer, and
greater in spring than in autumn ; but according to other
observers, it is greater in spring and summer than in autumn
and winter. Ozone has usually been found more abundantly
in the air at night than by day; but, again, some careful
observers have found the reverse of this statement to be true.
No connection has yet been proved to exist between the
amount of ozone in the atmosphere and the occurrence of
epidemic and other forms of disease.
Ozone is rarely found in the air of large towns, unless in a
suburb when the wind is blowing from the country ; and it is
only under the rarest and most exceptional conditions that it
is found in the air of the largest and best ventilated apart-
ments. It is, in fact, rapidly destroyed by smoke and other
impurities which are present in the air of localities where
large bodies of men have fixed their habitations.
The permanent absence of ozone from the air of a locality
may, however, be regarded as a proof that the air is adul-
terated air. Its absence from the air of towns and of large
rooms, even in the country, is probably the chief cause of the
difference which every one feels when he breathes the air of a
town or of an apartment, however spacious, and afterwards
inhales the fresh or ozone-containing air of the open country.
The amount of ozone in the atmosphere is extremely small,
and an excess of ozone is destructive to life; thus the
respiration for a very short time of oxygen containing about
i-240th part of ozone is certainly fatal to all animals ; whilst
similar animals will live in good health for months after
respiring oxygen alone for 37 hours, the carbonic acid being
removed during the experiment.
an Occupied Building. 41
The action of breathing and transpiring upon the air is
as follows : —
I. The oxygen is diminished.
%. The. carbonic acid is increased.
3. A large amount of watery vapour, is added.
4. There is an evolution of ammonia and organic matter.
5. A considerable amount of suspended matter is set free,
consisting of epithelium, and molecular and cellular
matter, in a more or less active condition of putrefac-
tion. At the same time, portions of epithelium are
constantly being given off from the skin, and even
pus cells from suppurating surfaces ; as, for instance,
with surgical cases in hospitals.
The oxygen is, of course, diminished in the direct ratio
of the consumption of carbon and hydrogen in the system.
As regards the amount of carbonic acid, a subsistence diet,
sufficient for the internal work of the body only, is a little
under 3000 grains of carbon daily, yielding about 13-6 cubic
feet, or about 0-57 cubic feet per hour of CO2.
Angus Smith, in his experiments, was unable to find more
than 0-4 per hour of- COg given off; but the experiments of
Pettenkofer showed that in a state of repose an adult gave off
about o«7, and in a state of active work 0*9 to i-o or more.
The constitution and usual diet of the person experimented
on no doubt influences the result.
These numbers correspond pretty closely with theoretical
calculation, but if the number 0'6 be taken to allow for differ-
ence of age, weight, and sex, it will be well within the mark
in the calculation.
The amount of vapour varies, but taking the amount from
skin and lungs together, it may be assumed at about 30 oz.
per diem, or about 550 grains per hour, enough to saturate
about 90 cubic feet of air at a temperature of 63° Fahrenheit.
The amount of organic matter has been variously estimated,
but there are hardly any trustworthy experiments on record.
42
Purity of Air in
As already mentioned, this organic matter is highly poison-
ous ; and it is as much from the presence of this as from
carbonic acid in re-breathed air that injury arises.
The air of towns is rendered impure chiefly from the
presence of suspended matters.
The experiments of Dr. Angus Smith show that in towns
the oxygen is not less than in the country districts, and that
carbonic acid is not materially in excess.
See the following table : —
In Manchester,
Oxygen.
In fog and frost . . .
Outer circle, not raining
Suburb, in wet weather
Per 1000
209*100
209*407
\ 209*800
( 209*600
CO,
Per 1000 vols.
Streets 0.403
Where fields begin . . . 0*369
Streets in fog 0*679
In London,
Oxygen.
Open places, summer .
Streets, November . .
209*500
208*850
CO
2
On Thames .
Parks, open .
Streets . .
0-343
0*301
0.380
It is therefore to other impurities that the oppression from
town air is attributable. For instance — The presence of sul-
phuric acid in the air is very noteworthy.
Numerous analyses of various sorts of coal showed that
whilst there was a mean of i«7 per cent of sulphur in the
several coals, no more than 0-% per cent remained in the ash.
Therefore the burning of 1000 tons of coals of this description
would send 15 tons of sulphur into the air as sulphurous acid ;
and this soon becomes converted into sulphuric acid ; this is
sufficient in quantity to render the rain water which is col-
lected in towns very frequently acid.
It has been estimated that the coal consumed in Glasgow
and its vicinity gives off sufficient sulphur acids to amount
to 300,000 tons of oil of vitriol annually. The quantity of
an Occupied Building. 43
coal estimated to be consumed annually in London is about
5,000,000 tons, which, from this calculation, would send into
the air 75,000 tons of sulphurous acid. London air contains
about 19 grains of sulphurous acid in a cubic yard of air. It
contains moreover, an enormous quantity of soot, fine carbon
and tarry particles of coal ; of the two latter almost I per
cent, is given off in combustion. This rarely rises above 600
feet from the ground. London air also contains much sus-
pended organic matter, independently of the sewer and other
emanations, and independently of the ammonia given out
by the manure of the enormous number of horses kept in
London. It is noteworthy that the mud from a paved street
in London was found on analysis to contain nearly 90 per
cent, of horses' dung ; the mud on the new wood pavements
consists almost entirely of horse dung^. In addition to such
matters town air contains vestiges of food, clothing, and
building materials ; as well as dust from manufactories.
An important cause of the impurity of air in town houses
especially arises from the use of coal-gas in rooms.
The products of the combustion of gas are carbonic acid,
carbonic oxide, compounds of ammonias, and various com-
pounds of sulphur, which are injurious to health.
The products of combustion vary much with the quality of
the gas and the completeness of the process, but 100 cubic
feet will unite with from 90 to 164 cubic feet of oxygen, and
produce iioo cubic feet of carbonic acid, and from %o to 50
grains of sulphuric acid, so that 100 cubic feet of coal-gas
consume the oxygen or destroy the vital qualities of 800 cubic
feet of air, and raise the temperature of 3i'a90 cubic feet of
air 100° Fahrenheit.
With imperfect combustion, 67 per cent, of nitrogen, 16 per
cent, of water, 7 per cent, of carbonic acid, and 5 to 6 per cent.
^ The wood pavement laid down in Regent Street about 30 years ago was re-
moved because it had become so saturated with ammonia that the emanations
tarnished the plate in silversmith^s shops.
44 Purity of Air in
of carbonic oxide, with sulphurous acid and ammonia, are
thrown into the atmosphere, but the quantity of carbonic oxide
will be materially reduced with more perfect combustion.
It follows that each cubic foot of gas burnt per hour may
be assumed upon an average to vitiate as much air as would
be rendered impure by the respiration of an individual.
An oil lamp burning 154 grains of oil per hour consumes
the oxygen of y% cubic feet of air, and produces a little
more than -5 cubic feet of carbonic acid. And a candle of
6 to the lb. burns about 170 grains per hour. The com-
bustion of these does not produce the compounds of sulphur
which result from the use of coal gas.
In the open country, the atmospheric currents continually
disperse the various substances thrown off in breathing.
The movement of the air is stated in the Registrar
General's reports to be about 1% miles an hour, on an average,
or rather more than 1 7 feet per second. It will rarely be
much below 6 feet per second.
Imagine a frame about the height and width of a human
body, measuring about 6 feet by li, or 9 square feet; multi-
plying this by the velocity of movement of the air at 6 feet
a second, it will appear that in one second 54 cubic feet, in
one minute 3^40 cubic feet, in one hour 196,400 cubic feet, of
air would flow over one person in the open.
In a room the conditions are very different. In barracks,
in a temperate climate, 600 cubic feet is the space allotted by
regulation to each soldier; and when in hospital from 1000
to iJ5oo cubic feet to each patient.
If it were desired to supply in a room a volume of fresh air
comparable with that supplied out of doors, it would be
necessary to change the air of the room from twice to six
times in every minute, but this would be a practical impossi-
bility ; and even if it were possible, it would entail conditions
very disagreeable to the occupants.
It is thus evident that when considering the condition of
an Occupied Building.
45
air indoors, it is necessary to seek a standard of admissible
impurity in the air, rather than a standard of purity of air,
comparable with that which exists out of doors.
In judging of the amount of impurity which may be allowed
in an inhabited air-space, the sense of smell, when carefully
educated, affords the best indication of the relative purity and
impurity of different kinds of aih
The accompanying table obtained from results of experi-
ments communicated by Dr. de Chaumont to the Royal
Society shows the conclusions at which he arrived from a very
large number of observations on the air of barracks and
hospitals. The method employed in judging of the quality
of the air was to enter directly from the open air into the
room in which the air was to be judged, after having been at
least 15 minutes in the open air. It will be seen how closely
the state of the room, as detected by the sense of smell,
agrees with that which would be expected from the carbonic
acid as shown by analysis.
Sense of Smell.
Temperature.
Vapour.
Carbonic Acid per
1000 volumes.
In air
space.
Excess
over
outer
air
In air
space.
Excess
over
outer
air.
In room.
Excess
over outer
air.'
Fresh
A little smell
Close or disagreeable smell .
Very close, or offensive and )
oppressive smell . , . j
Extremely close, when the J
sense of smell can no longer >
differentiate )
62.85
62.85
64.67
65-15
65-05
5-38
8.00
12.91
13-87
13-19
4.629
4.823
4.909
5.078
5-194
0.344
0.687
1.072
1.409
I-319
0-5999
0.8004
1.0027
1-3335
1
1.2818
0.1830
0.3894
0.6322
0.8432
0.8817
In these experiments. Dr. de Chaumont takes •oooiz of
carbonic acid per cubic foot as the standard of impurity, in
addition to -0004 carbonic acid per cubic foot as the normal
amount of CO2 in the outer air.
The experiments were made in barracks and in hospitals.
46 Purity of Air in
and a result came out from the experiments confirmatory of
the opinion that, in the case of sick men, more air is required
to keep the air space pure to the senses than is necessary in
the case of men in health. It appeared that, in barracks, the
mean amount of respiratory carbonic acid, when the air was
pure to the senses, was •196 per 1000 volumes, but in hospitals
it was only '157 ; or, in other words, whilst in the hospitals the
air would have smelt somewhat impure when the COg was
•157, in the barracks with that amount, it was fresh.
On these grounds it would therefore appear that whilst the
standard for impurity for healthy persons may be regulated
by allowing an excess of •ooo!Z per cubic foot of COg over
that in the outer air, it would be desirable to limit the excess
in the case of sick to •00015 per cubic foot.
In addition to the proportion of carbonic acid, and of the
impurities of which its presence affords a rough test, there are
conditions of temperature and humidity necessary for good
ventilation.
Temperature. The dry bulb thermometer in this climate
ought to read 6'^ F. to 6^ F., and ought not, if possible, to
fall much below 60° F,
The wet bulb ought to read 58° F. to 6i° F. That is
to say in this country the difference between the two ther-
mometers ought not to be less than 4° F. or more than
8° F. A greater degree of dryness in the air, provided the
supply of air be ample, is not however found objectionable.
In the open air, in healthy weather, it is often 8° or 9° or
more. The difference is of course increased in hot and dry
climates.
Vapour ought not to exceed 4*7 grains per cubic foot at a
temperature of S'^^ or 5-0 grains at a temperature of 6^ F.
The limit of humidity is 75 per cent, or under.
When the outer air is saturated, as in wet weather, the
reduction of the humidity in a room will depend on the
increase of temperature of the air admitted.
an Occupied Btnlding. 47
The capacity of the air for moisture increases enormously
with the temperature, and that which would saturate air at
50° F. would give only 71 per cent, at 60° F. Thus, at 50° F.
a cubic foot of air is saturated by 4«i grains; but at 60° F.
it requires 5-8 grains, so that 4-1 grains would give only
71 per cent.
If therefore the outer air is at a temperature of 50°, and if
the temperature inside the room be maintained at a comfort-
able standard, say 6^ to 6^"^^ the incoming moisture would
never cause an excess of humidity.
In the case of an external atmosphere, saturated at or above
the temperature within, such as occurs occasionally in hot
climates, it would be necessary to let in an unlimited quantity
of air through every possible aperture.
vl' .^
CHAPTER VI.
CUBIC SPACE AND FLOOR SPACE.
The purity of the air within an inhabited space, enclosed
on all sides, is necessarily vitiated by the emanations pro-
ceeding from the bodies of those who inhabit it, and especially
by the effect on it of their respirations. With persons
suffering from disease, especially infectious fevers, or from
wounds, or sores, these emanations are greater in quantity
and more poisonous in quality, than from persons in health.
Stagnation in the movement of the air would lead to rapid
putrefaction of these emanations.
Vitiated air does not necessarily mix with the whole air of
the room with rapidity. Any one may satisfy himself of this
by comparing the upper part of a heated room with the
lower, or by examining outlets for the escape of air. The
top of a room will sometimes be found to contain much more
carbonic acid than the lower part. Therefore under certain
conditions the law of diffusion does not act so rapidly as to
prevent an occasional difference between the amount of COg
in the upper and the lower air of a room ; the organic emana-
tions diffuse themselves more slowly, and without absolute
uniformity, and are deposited on the cool walls, ceilings, floor,
and furniture, where they may be easily collected if desired.
It would be desirable, if it were practicable, to remove the
exhalations with such rapidity as to prevent deposition, and
to permit as little admixture as possible with the air of the
room ; but this is not practicable.
and Floor Space. 49
In considering theoretically the condition of a room in
which sources of impurity exist, and which is furnished with
any kind of ventilating arrangements, tha two extreme suppo-
sitions (both inadmissible) are
(i) That all exhalations are immediately removed com-
pletely out of contact of the persons in it, so that the occupants
of the room are in the same condition as to purity of air as if
they were out of doors in a brisk wind.
(2) That the ventilation is so unequal that the spaces
immediately surrounding the persons do not get ventilated at
all ; and that the occupants of the room practically live in an
air which may become saturated with noxious matter.
The actual state of things must be something between these
two. And it is probable that the best condition actually
attainable would approximate, not very closely, but still in
some tolerable degree, to the ideal condition in which all
diffusible emanations should be instantaneously and uniformly
diffused through the whole space.
Now, supposing this ideal condition to subsist, it is perfectly
easy to show that the degree of purity of the air would ulti-
mately depend in no way on the size of the room, but solely
on these two things, viz. (a) the rate at which emanations
are produced : (/3) the rate at which fresh air is admitted.
Demonstration ^.
Suppose P units of diffusible poison are produced per
hour.
Also suppose A cubic feet of air introduced per hour.
The same number must necessarily escape per hour.
The condition of the room having become permanent, the
quantity of poison escaping is the same per hour as the
quantity produced (otherwise the condition of the room
would be changing).
* By the late Professor Donkin of Oxford.
E
50 Cubic Space
Hence P units of poison escape per hour ; and since this
quantity is carried away in A cubic feet of air, the escaping
P . .
air necessarily contains -j units of poison per cubic foot, what-
ever be the size of the room. The escaping air may or may
not be a sample of the average of the room. On the sup-
position of uniform diffusion^ it is a sample ; hence : —
On the supposition of uniform diffusion, the air in the room
p
ultimately contains -^ units of poison per cubic foot, whatever
be its size. Thus, on this supposition, the final condition of
the air depends only on the rate of production of poison, and
on the rate of admission of fresh air^ and in no way on the
space.
But if the mode of ventilation be bad, the diffusion will not
be uniform; and not only so, but there is theoretically no
limit (except that of saturation) to the quantity of poison
which may remain as a constant quantity in the room,
however abundant may be the supply of fresh air.
It seems hardly conceivable, though it is mathematically
possible, that the whole quantity of poison remaining per-
manently in the room could be reduced by any contrivance
below that of uniform diffusion.
The condition referred to above, as permanent^ is a state
which, theoretically, would never be actually attained, but to
which the actual condition would continually approximate as
a limit.
Suppose, as before, that P units of poison are produced in
the room per hour when it is occupied. Suppose also that
the fresh air itself contains / units of poison per cubic foot.
Let c be the number of cubic feet in the room ; and suppose
that at a given time the room begins to be occupied, and that
A cubic feet per hour of fresh air are introduced, so that the
same volume of air per hour also escapes.
Then, if x be the number of units of poison per cubic foot
and Floor Space. 51
in the air of the room at the end of t hours, it can be shown ^
(see demonstration below) that on the hypothesis of uniform
diffusion
where e is (as usual) the number a«7i8. The numerical
value of the last term in this expression diminishes rapidly
as / increases, and will become insensible after a number of
hours depending on the ratio oi A to c. Thus the quantity
of poison per cubic foot increases continually from the initial
^ Demonstration of the formula used above.
C « content of room in cubic feet.
A •- number of cubic feet of fresh air introduced per hour.
P = number of units of poison produced in room per hour.
p — number of units of poison in a cubic foot of fresh air.
/ B time (in hours) since beginning of occupation.
X B number of units of poison per cubic foot in the room at time /.
During the next instant dt, Adt cubic feet of air are introduced, and the same
quantity escapes.
The escaping air contains x units of poison per foot, so that Axdt is the quantity
of poison which escapes.
During the same instant, Apdt units are introduced with the fresh air, and Pdt
units are produced in the room. Hence the whole increase of poison in the room is
{P'\'Ap^Ax)dt,
but the increase per cubic foot is dx^ so that the whole increase is cdx ; hence
cdx = (P + Ap—Ax) dt.
Integrating this equation, and determining the constant of integration by the
condition that x = p when / = o, we obtain the expression for x given above.
The following may be added.
Suppose a room of c cubic feet, containing initially n' units of poison per cubic
foot, to be shut up for t hours with a man in it who produces P units per hour.
At the end of that time, how much fresh air (containing p units per cubic foot)
must be added to the air of the room in order to reduce the quantity of poison
per cubic foot to v units?
It is easily found that the number of cubic feet required is
c(v'—v) + Pt ^
w^p '
and this formula shows clearly that if v « v, that is, if the room is to be brought
back to its initial condition, the quantity required is independent of c, that is, of
the size of the room.
This demonstration was furnished by the late Professor Donkin of Oxford.
£ 2
52 Cubic Space
P
value pi and tends to the final or permanent value / + -2" *
which it will attain sensibly after a finite number of hours,
though never rigorously.
The size of the room then does not affect the permanent
condition of the air ; but everything else being the same, the
larger the room is, the longer it will be (after beginning to be
occupied) before it attains sensibly its final or permanent
condition of impurity.
If, in the final condition, the number of units of poison per
p
cubic foot be tt, then tt =/ -f — i
whence A = >
TT — /
which gives the number of cubic feet of fresh air per hour
required to maintain this condition.
For example ; suppose a man produces 6 units of carbonic
acid per hour, and fresh air contains •004 such units per cubic
foot, if it is required to maintain a room (of whatever size),
constantly occupied by one man, in such a condition that the
units of carbonic acid in a cubic foot shall never exceed '006,
then A == — ^ = 3000,
.006— .004 ^
that is, 3000 cubic feet of fresh air must be supplied per hour.
In this case, at the end of / hours after the room begins to
be occupied, the number of units of carbonic acid per cubic
foot is , 3>ooo<
.000 — 002 X € T"'
where c is the number of cubic feet of space in the room.
Thus, suppose the room contains 1000 cubic feet of space,
then the units of carbonic acid per cubic foot are
at first *oo4,
after i hour .... -005900,
„ a hours .... '005995,
•I 3 w .... -0059997 ;
and Floor Space. 53
so that after two hours the room would have sensibly reached
the final condition of '006 units per cubic foot. If the room
contained only 100 cubic feet of space, the approximation to
the final state would be much more rapid.
In considering the question of purity of air in an enclosed
space, it is necessary to take into consideration the sources
of vapour inside the room. Every man gives off from lungs
and skin each hour enough to raise the humidity from 70 per
cent, to complete saturation in 500 cubic feet at 60° F., and
to raise it to 82 per cent, in 1500 cubic feet. Now to reduce
this amount to 73 per cent, would take 3000 cubic feet of air
saturated at 50° F. But the vapour given off by the body is
not the only source of humidity. Humidity may arise from
the combustion of lights, or the vapour of liquids used in the
room.
According to this theoretical assumption of temperature
and moisture, a room containing an air space of 1000 cubic
feet, occupied by one individual, would require to be supplied
with 3000 cubic feet per hour, in order to maintain it in a
proper condition of purity and humidity.
Thus, upon the assumption made, the theoretical calcula-
tions, based first on carbonic acid, and secondly upon humidity,
lead to similar conclusions in each case.
In a warm climate the natural changes of temperature, and
consequent alteration of the conditions of the movement of
air, differ widely from those in temperate and cold climates.
In warm climates these figures may be applicable.
But in our temperate climate, a careful practical examina-
tion of the condition of barrack-rooms and hospitals, judged
of by the test of smell, shows that arrangements which appear
to provide for a volume of air much less in amount than
that obtained by calculation will keep the room in a fair
condition.
These results have pointed to about 1 200 cubic feet of air
admitted per hour in barrack'-rooms occupied by persons in
54 Cubic Space
health. This need not be set down to errors in calculation or
in theory.
There are many data which cannot be brought into the
theoretical calculation.
For instance, the carbonic acid disappears in a newly-
plastered or lime-washed room, and could be recovered from
the lime, therefore a newly cleaned lime-whited room will
present different conditions from a long occupied dirty room.
Quicklime washing destroys fungi in dirty walls, as also does
sulphurous acid fumigation. Now air has the jsame property,
especially dry air ; and hence opening windows, turning down
beds, and all such measures, act directly on the subsequent
state of the air. Therefore an enormous effect is produced on
all the elements of the above calculation if the windows of a
room are kept open for several hours a day, instead of being
closed.
Besides this, the conditions under which the air flows in and
out of a room are so varied. The walls and ceiling themselves
allow of a considerable passage of air. Examples of the
porosity of materials have been already given. The ceiling
affords a ready instance of porosity ; an old ceiling is black-
ened where the plaster has nothing over it to check the passage
of air, whilst under the joists where the air has not passed so
freely> it is less black. On breaking the plaster, it will be found
that its blackness has arisen from its having acted like a filter,
and retained the smoky particles while the air passed through.
Moreover, the porosity of the walls materially influences the
moisture, for a porous wall may absorb much moisture ; and
on this account rooms with walls of polished impervious
material require much more air to pass through them. In the
absence of sufficient ventilation, when the walls are colder
than the air, moisture condenses on the walls.
Ill-fitting doors and windows allow of the passage of a
considerable quantity of air.
In a temperate climate, where the changes of temperature
and Floor Space. 55
of the outer air are rapid and considerable, these means of
producing the outflow of air from and the inflow of air into a
confined space are in constant operation. A sleeping-room is
very warm when occupied at night ; a rapid fall of tempera-
ture occurs outside, and at once a considerable movement of
air takes place.
The majority of occupiers of sleeping-rooms in England
close their windows at night; they also often block up the
chimney by a register or otherwise, to prevent the blacks
falling. These rooms have no special inlet or outlet for
changing the air. In the morning they would no doubt come
under Dr. de Chaumont's definition of ' very close ' ; and if it
were not for the continual insensible change of air which
passes through the walls, and the door and window chinks,
&c., the occupants would be asphyxiated. A well-built house,
unprovided with special means for the inflow of fresh air, is
from the very completeness of construction a real source of
danger.
For these reasons, the form of a building is important,
especially where rooms have to be occupied by large numbers
of persons.
The air, thus insensibly coming in, should be taken from
pure sources. Thus, barrack-rooms with outside walls are
better than rooms opening out of a corridor, or on each side
of a corridor. The air in a corridor becomes, after a time,
saturated with impurities, and the interchange of air from it
to the barrack-room becomes in time only an interchange of
impure air. This is especially noteworthy in hospitals, where
fresh air is of even more importance. The following Fig. 4
shows an arrangement of barrack-rooms built little more than
twenty-five years ago, which illustrates this point ; the outer
wall is only a quarter of the whole wall-space.
Fig. 5 shows the form of rooms which have been adopted in
all recent barracks, in accordance with the principles here laid
down. In this case the windows afford means for sweeping
56;
Cubic Space
the bad air out of the room, so that the occupants shall have
the opportunity of starting every day with fresh air ; while
the length of wall exposed to outer air, as compared with the
inside walls, is as four to one.
Fig. A-
These considerations bear essentially upon the construction
of buildings occupied by lai^e numbers of persons, such as
barracks, workhouses, schools, or asylums ; but they are
especially applicable to hospitals, where, as has been already
Fig. 5-
shown, the emanations from a given number of sick are more
perceptible than those from individuals in health j and for
this reason, in addition to numerous other reasons, the pa-
vilion form of hospital construction presents advantages over
other forms. In private dwellings the same conditions of
occupation do not prevail ; and in these, therefore, considera-
and Floor Space. §7
tions of comfort, and convenience of internal arrangement, may-
be allowed to have more weight in the design than the outer
form of the building.
The foregoing observations will have shown that whatever be
the cubic space, the air may be assumed to attain a permanent
degree of purity^ or rather impurity, theoretically dependent
upon the rate at which emanations are produced, and the rate
at which fresh air is admitted ; and that therefore the same
supply of air will equally well ventilate any space, but the
larger the cubic space, the longer it will be before the air in it
attains its permanent condition of impurity. Moreover, the
larger the cubic space, the more easily will the supply of fresh
air be brought in without altering the temperature, and with-
out causing injurious draughts.
One of the chief difficulties of ventilation arises from the
draughts occasioned thereby. Every one approves of ventila-
tion in theory ; practically no one likes to perceive any move-
ment of air.
Large rooms, in addition to the advantage afforded of
enabling the air to be changed with more comfort to the
occupants than small rooms, also present the advantage of a
larger wall-surface, and of more numerous windows, which
allow of a larger insensible ventilation ; thus larger rooms will
have, even in proportion to their occupants, an apparently less
degree of impurity than small rooms. Although the uniform
diffusion of carbonic acid is comparatively rapid in the air of
a room, the organic emanations given out do not in practice
diffuse themselves either rapidly or uniformly. They hang
about in corners where there are obstructions to the flow of
air, or near the ceiling, in which case they cool and fall down,
and mix with the air of the room, thus increasing the im-
purities in the lower part of the room. Consequently there is
no advantage in mere height in a room unless combined with
means for removing heated air from the upper part. Indeed
a lofty room with a space above the top of the windows or
58 Cubic Space
ventilating openings to which air loaded with emanation can
ascend, remain stagnant, cool, and then fall down, is a positive
disadvantage.
In a room with more than one occupant, it is necessary
that a certain floor-space should be allotted to each occupant,
for the purpose of allowing the currents of air to remove the
emanations from one occupant without interfering with his
neighbour, and to prevent the inconvenience of too close
juxtaposition. The cubic space for soldiers in barrack-rooms
occupied by day and night was fixed by the Royal Com-
mission of 1 858 at 600 cubic feet per man ; if we assume a
room to be i:? feet high, that allows 50 superficial feet per
occupant, and if the room be 20 feet wide, with beds on each
side, the width across each bed, that is the linear bed-space,
would be 5 feet.
In a room 10 feet high and 20 feet wide, a width of 6 feet
of linear bed-space would be afforded ; but with rooms higher
than 12 feet, it would be unadvisable to diminish the floor-space ;
thus the floor-space necessarily to some extent governs cubic
space. In warm climates a larger cubic space is given, mainly
with the object of obtaining a larger floor-space. In some
cases as much as 80 feet of floor-space per occupant has
been given in barracks, dependent on local conditions of the
healthiness of the site, and of the plan of the buildings.
The Royal Commission on Cubic Space in Workhouses
considered where so many persons have to be lodged at the
expense of the ratepayers, it was necessary to exercise the
most rigid economy of space, and to supplement the deficiency
of space by the strictest attention to ventilation and warming ;
and they reported, that for dormitories in workhouses occupied
only at night by occupants in health, 300 cubic feet would be
sufficient, provided the wards did not contain more than two
rows of beds, and that the height, if above 12 feet, was not
reckoned in the calculation. This would allow a minimum
floor-space of 25 feet per occupant, or with dormitories 17 feet
and Floor Space. 59
wide, a bed-space of about 3 feet. This allowance is based
upon the assumption that the most watchful care is bestowed
on the efficiency of the ventilation.
In ordinary hospitals the cubic space is practically de-
pendent on the floor-space, for on this depends the distance of
the sick from each other, the facility of moving about the sick,
shifting beds, cleanliness, and other points of nursing. If
there be a medical school attached to the hospital, the
question of area has to be considered with reference to
affording the largest amount of accommodation practicable
for the teacher and his pupils.
A ward with windows improperly placed, so as not to give
sufficient light, or where the beds are so placed that the nurse
must necessarily obstruct the light in attending to her patients,
will require a large floor-space, because the bed-space must be
so arranged, and of such dimensions, as to allow of sufficient
light falling on the beds. In well-constructed wards with
opposite windows, the greatest economy of surface area can
be effected, because the area can be best allotted with re-
ference both to light and to room for work.
In a ward %4 feet in width, with a window for every two
beds, a 7 feet 6 inch bed-space along the walls would probably
be sufficient for nursing purposes. This would give 90 square
feet per bed, and there should be as little reduction as possible
below this amount for average cases of sickness; but this
space is too small for fever or lying-in wards.
The practice in regard to area differs considerably in dif-
ferent hospitals. In the naval hospitals it is about 78 square
feet per bed. In the Herbert Hospital, where there is no
medical school, it is 99 square feet per bed. The cubic space
which results from this, with wards 14 feet high, is 1160 cubic
feet.
In the Royal Victoria Hospital at Netley, where there is a
medical school, it is 103 square feet. In St. George's Hospital
it is about 70 square feet.
6o Cubic Space
From this minimum, it varies to 138 square feet in Guy's
Hospital. In the new H6tel Dieu, at Paris, the space per bed
is from 104 to no square feet, and in the new St. Thomas's
Hospital it is 112 square feet. This latter area is considered
sufficient both for nursing and teaching purposes.
In fever hospitals, and in wards for bad surgical cases, where
the emanations from the patients are considerable, it is found
desirable to afford a larger floor-space, varying from 150 to
200 superficial feet, or occasionally more, according to the
position and shape of the structure; and this entails an
enlarged cubic space.
In cases of fever, if a separate ward is not available, a bed
should be removed on each side of the fever patient.
The most recent form for lying-in wards adopted in Paris is
for each patient to be placed in a small separate room, about
T a X 14 and 1 1 feet high, opening through a lobby to the open
air; each room being provided with a small scullery, also
opening into the lobby. The waste pipe from the sink dis-
charges with an open end over a trapped gully out of doors,
and all foul refuse is received in moveable receptacles and
removed at once.
These rooms are left vacant, and with open windows and
doors for a certain time after each occasion of being used.
On the other hand, in workhouse hospitals, where the
strictest economy is sought, and where the cases are generally
of a more chronic character than in ordinary hospitals, the
Royal Commission on Cubic Space in Workhouses required
850 cubic feet per inmate, with a minimum of 70 square feet
of floor-space, and a clear space of six feet across each
bed, and that no bed should be placed in the middle of the
floor.
In special workhouse hospitals for fever and small-pox
patients, 3000 cubic feet, and a minimum floor-space of 166
square feet, is provided.
For lying-in wards in workhouses a minimum of 1200
and Floor Space. 6i
cubic feet and ico square feet is the standard ; but these wards
in workhouses are seldom continuously occupied.
In wards partially occupied by day and by night for aged,
chronic, and infirm cases, with the use of a day-room, 500
cubic feet and 42 superficial feet were specified as necessary.
These sizes were adopted upon the condition that the
ventilation would be adequate and carefully watched.
It will thus be seen that the question of floor space in a
hospital ward must be settled with reference to the existence
or non-existence of a clinical school in the building, and the
number of pupils likely to follow the medical officer. Excluding
a medical school, and assuming that the locality of a hospital is
healthy, the floor-space may be fixed at about 90 square feet
per bed in this climate, with the understanding that the area
shall be increased if the building is designed for a medical
school, or where from unavoidable circumstances an unfavour-
able site must be selected.
Dormitories in schools should certainly not afford less floor-
space than from 50 to 60 square feet. In prison cells, where
the prisoner is confined continuously, the superficial area per
occupant should not be less than from 80 to \%o feet, accord-
ing to the character of the prison and other circumstances.
In the case of rooms occupied in the day-time, or for a
portion of the day only, such as day-rooms in hospitals,
workshops, or schools, a smaller cubic space is sufficient.
The reason is obvious. In the case of schools, for instance,
the occupants leave the room empty occasionally, so that the
air can be periodically renewed.
Thus the proportion of floor-space and cubic space in any
room must be regulated to a certain extent with reference to
its shape and to the conditions of its occupation, as well as to
its capacity for ventilation.
CHAPTER VII.
MOVEMENT OF AIR.
Air of the composition before mentioned, viz. aio of
oxygen to 790 of nitrogen, is a heavy body. At a tem-
perature of 3^°, and with the barometer at 30 inches, which
is about the mean sea level, dry air weighs 5^6*85 grains per
cubic foot. The pressure of the atmosphere on any surface
is nearly 14*7 lbs. to the square inch ; and a column of air of
about 87«6 feet in height, under these conditions, will balance
a column of mercury •! (or one tenth) of an inch in height.
The molecules of air are but feebly attracted to each other,
and small increases of temperature, or slight diminutions of
pressure separate the particles from one another, and thus
one cubic foot of expanded air weighs less. Similarly, small
decreases of temperature bring the particles nearer together,
and make the 'cubic foot of cold air heavier than the standard
above mentioned. This expansion and contraction are equal
for equal increments or decrements of temperature.
This increase of volume amounts to 0-365, or about three-
eighths of the original bulk, in the process of being heated
from the freezing to the boiling point of water ; or nearly
•00203 for every degree of Fahrenheit.
Thus, if the air inside a room were 20^ Fahrenheit warmer
than the air outside, the air in the room would be expanded
to a iZ5t^ part more in bulk, and would to that extent be
specifically lighter than the outside air.
This dilatation of air by heat and its contraction by cold
are expressed by the formula Mi = (i-^at) M
Movement of Air,
63
when M = volume at 3^® and the barometer at 30 inches,
M-i = volume at the temperature of t degrees above 32^
a = co-efficient derived from experiments on the pro-
portion of the increase of volume of air for each
degree of elevation of temperature ( = •00203 for
each degree of Fahrenheit).
When temperature is decreasing the formula is
M^-{\-at)M.
When the temperature of air and the space it occupies
increases, its density, that is its weight per cubic foot,
decreases in the ratio expressed in the following formula,
assuming barometric pressure constant,
The following table shows the density of air at different
temperatures,^
Weight of air per cubic foot under 30 inches
pressure of Mercury.
Temperature
Fahrenheit.
Dry Air.
Air saturated with
vapour.
Grains.
Grains.
0°
60637
606.03
20«
S^i-os
580.26
32°
566.85
565-58
40-
557-77
556-03
50^
546.82
544-36
60^
536-28
533.84
80°
516.39
509.97
100°
497-93
486.65
It follows that since warmed air expands and becomes
lighter, and since cooled air contracts and becomes heavier,
^ The weight of a cubic foot of air at different temperatures and pressures may be
found approximately by the formula weight in lbs. »
1.3253 X Height of Barometer in inches of mercury
459 + Temperature Fahrenheit
64 Movement of Air.
the colder air has a tendency to press upwards the warm and
lighter air, and to occupy the place of the warmer air. In an
enclosed space, the rate at which the warmer air will thus
be pressed upwards by the inrush of colder air, and be forced
out, will depend upon the form, size, and materials of the
openings which permit its escape.
Everywhere the heating and cooling of the air is going on ;
the sun's rays, the proximity of a warm body, the vicinity
of a cool shaded surface, all cause changes of temperature,
and thus create movements or currents in the air.
In a room, as air is warmed by the bodies of the occupants,
it ascends ; it comes in contact with the walls of the room or
with the glass of the windows ; it cools, and falls down. A
draught experienced near the window, does not necessarily
show that air is coming in through the window, it may simply
result from the cooled air which is falling.
It is on this law of the dilatation of air that all the move-
ment of air depends, from the winds and hurricanes to the
ventilation of houses, except where air is propelled by fans or
by other mechanical appliances.
It is also noteworthy that the air saturated with vapour is
lighter than dry air, and air will therefore flow upwards more
easily in proportion as the ascending column is saturated with
vapour ; and therefore breathed air which contains moisture
from the occupants of a room ascends more easily than the
drier unbreathed air.
The law which regulates the movements of the air in a con-
fined space, when the temperature is higher than that of the
outside air, depends upon the following considerations : —
I. Upon the difference of temperature of the air inside the
confined space, as compared with that outside.
a. Upon the area and other conditions of the apertures
through which the warmed air can flow out and the cooler
outside air can flow in to take its place.
3. Upon the height of the column of ascending warmed air.
Movement of Air. 65
If AB represent the height of a column of air of the outside
temperature Z^, and A C the height of a column of the same
quantity of air expanded by the warmer temperature /, then
the velocity at which the warmer air ascends will be that
which would be acquired by a body falling from C to B.
C-T-
B
That is, V = ^/^g x BC,
if F = velocity of ascending air in feet per second ;
H — height of shaft in feet ;
/ = temperature in shaft ;
ty = temperature out of doors ;
a = the coefficient of dilatation of air, which for 1° Fahren-
heit = •002036 ; and for 1° Centigrade = •003665 ;
^=3^-i7^
The theoretical equation becomes F= ^^igHa^t^t^,
Therefore the velocity, and consequently the volume of air
varies with the square root of the difference between the
temperature inside and outside the shaft.
The actual movement of air in a chimney is very different,
owing to the resistartce from friction to which the moving air
is subjected. The friction varies directly with the square of
the velocity of the air-currents, and with the length of the
channel or flue, and inversely with the diameter or area of
the flue ; and is, moreover, much influenced by the material
of which the sides of the flue are constructed. With a sooty
flue, or a flue with rough sides, the velocity, with equal tem-
peratures, has been found to be one-half that of a smooth
clean flue.
The velocity is, moreover, diminished by the friction caused
by impediments to the ingress of the fresh air required to
supply the place of that which flows out; and therefore an
efficient system of ventilation requires that the extraction of
F
66 Movement of Air,
air should be accompanied by convenient arrangements for
the supply of fresh air to take its place, and vice versA.
If these resistances be represented by the constant K^ to be
determined for each case depending on the (orm and material
of the shafts and air-channels, and on other considerations,
such as their freedom from dirt, &c., the formula may be
generally expressed as follows —
P^clet, in his treatise on the application of heat, has given
the following formula to include some of the resistances —
" D+2gHK '
when Z> = diameter of shaft, circular flue, or square root of
area of rectangular flue ; K = the coefficient of resistance.
And he determined the coefficient of resistance, correspond-
ing to this formula, due to pottery chimneys to be •0127 ; sheet-
iron chimneys to be -005 ; and cast-iron chimneys to be •0025.
This formula gives rather too high results. Phipson suggested
"" Z-hi6Z>
where L = length of evacuation channels. Hurst gives
^ " n-\^KL '
where the dimensions are in feet, and K = -02 for clean glazed
earthenware flues, -03 wood flues, -06 sooty flues. The diffi-
culty of obtaining a uniform coefficient for the resistances will
be made apparent from the fact that in flues of the size of
ordinary chimneys, soot or accumulations of dust on the sides
seriously affect the velocity ; General Morin found that the
presence of a cobweb in a flue almost entirely checked the
passage of air. The main conditions to be attended to in
the design of air channels are that they should be as straight
as possible, with smooth sides, and with such an area as will
prevent the necessity of maintaining a high velocity in the
channel.
Movement of Air, 67
The circumstances which affect the flow of air are thus so
varied that it is preferable, in estimating the amount of air
removed for purposes of ventilation from buildings already
constructed, to measure the actual volume of the air in the
flues or air-passages ; that is to say, to cause it to pass along
a channel — the size and area of which are known — and then
to measure the velocity with which the air passes through
this channel. The multiple of the area into the velocity in
a given time gives the volume which passes through in that
time.
There are various ways of measuring the velocity. It may
be measured by puffs of vapour of turpentine ; by balloons
filled with hydrogen, and weighted to be of the exact specific
gravity of air. In ordinary cases, the most convenient
method is by means of an anemometer. An ordinary form of
anemometer is that of vanes fixed to a spindle, the revolutions
of which are recorded by a counter. The vanes are turned
by the direct action of the current of air, and the number of
revolutions which are recorded by the counter gives the
velocity. Of course the value of these revolutions has to be
ascertained in the first place by direct experiment; that is,
by forcing a known bulk of air, at a uniform rate, through
a channel of a given size ; and ascertaining the number of
revolutions made by the vanes. The most convenient ap-
paratus for this purpose is a graduated vessel constructed on
the principle of the ordinary gas-holder, arranged to move
with a uniform speed, from which a known quantity of air can
be expelled at will through a channel of convenient dimen-
sions in connection with it.
For anemometers of this pattern the formula which must be
applied to ascertain the velocity takes the following form —
where V = velocity of air ;
« = a constant number showing the minimum speed
of current which will move the vanes, and which,
F %
68 Movement of Air.
sHould be contrived to be as small as possible,
* by means of light vanes and delicate m.achinery ;
3 = a constant coefficient ;
N = number of turns of the spindle in i second.
Fletcher's Anemometer is another very convenient form for
measuring the speed of air in heated flues.
The instrument consists of two parts ; firstly, of two metal
tubes of about ^rs of an inch internal diameter, open throughout,
and of any length ; secondly, of a manometer, or pressure-
gauge. Of these tubes, the end of one is straight and plain,
while that of the other is bent to a right angle. When in
use these tubes are placed parallel to each other, and so that
their ends are exposed to the current of air to be measured.
They lie at right angles to the current, which thus crosses the
open end of the one, and blows into the bent end of the
other.
By this means a partial vacuum is established in the
straight tube, whilst the pressure of the current forces the air
into the bent tube ; a differential manometer, attached to the
outer ends of the tubes, shows the excess of pressure in the
bent one over that in the straight one. The manometer
used is a simple U-tube set vertically, containing ether, fitted
with microscopes and vernier scales, by which the difference
of level of the surfaces of the ether in the two limbs can
be measured to j^Vtt of ^"^ inch. This difference of level
between the columns of ether becomes a measfure of the
speed of the current passing the ends of the anemometer
tubes ; the law which governs the speed is expressed generally
by the formula «/ = v''/x28».55 The corrections to be made
for small variations of barometric pressure and temperature
Movement of Air. 69
are unimportant. The corrections when required are em-
bodied in the following formula —
A
39-92 459+^
where p is the height of the column of liquid driven up the
tube measured in inches, and v is the velocity measured in feet
per second of air at a temperature of / degrees Fahr., under
a pressure of h inches of mercury.
Tables of the velocities corresponding with the readings are
supplied with the anemometer, and also a table of correction
for temperature.
The variations of temperature to which the manometer
Itself is exposed are not great, being those of the external
atmosphere only.
This is a very convenient form of anemometer, because the
pressure-tubes may be of any length or diameter, and may be
connected with the manometer by india-rubber tubing of any
length. Therefore the readings may be observed in any
convenient place at a distance from the flues.
The pressure-tubes should project into the air-current to
the extent of one-sixth part of its diameter, to measure the
average velocity. It is desirable, after observing the height of
the ether in the tube, then to reverse the connection with the
manometer, and to take a second reading; if the smaller
reading be deducted from the greater, twice the height of
the column supported by the difference of pressure is ob-
tained, and the error of observation is halved. But in this,
as in the anemometer with vanes, there is a difficulty in
accurately observing low velocities, i. e. under i foot per
second.
It is worth noting that a sheet of light tracing-paper moved
through the air at 2 feet per second takes up an angle of 45°,
and affords a ready means of measuring that velocity; and
for smaller velocities the angle assumed by the flame of a
70
Movement of Air.
candle affords a fairly accurate index according to the follow-
ing table.
Velocity of flow
of air.
Feet per second.
Angle of inclination
of flame of candle
with horizon.
16
30=
I^
40°
0-75
S0°
0.50
60°
.40
6S°
In a shaft open at the top, containing air at a temperature
above that of the outside air, and in which means exist for
keeping the incoming air at a similar uniform temperature
above that of the air outside, the velocity of the upward
current will vary with the height of the shaft. In order,
therefore, to effect the extraction of the air in an enclosed
space with the least expenditure of heat, the shaft should be
made as high as possible. Any diminution in height or in
area piust be compensated for by additional heat in the shaft ;
this means an additional consumption of fuel to keep up the
temperature.
Therefore the economical application of the law of dilatation
of air depends on the height available for the shaft, upon its
area, and upon its being as free from friction and other resist-
ances as possible, and upon the difference of temperature
which can be obtained indoors and out. It will thus to some
extent depend upon climate : where the outer air is cold, and
a comparatively high indoor temperature must be maintained
for comfort, it is most economical ; but where the difference
between the indoor and outside temperature is small it is
less economical. Thus General Morin found that whilst in
winter the ventilation in the Conservatoire des arts et metiers
by extraction-shafts was continuously maintained with an
expenditure of i lb of fuel for 8700 cubic feet of air removed,
in summer i lb of fuel removed only 3000 cubic feet.
Movement of Air. ji
Arrangements for the change of air in a confined space
which depend on difference of temperature are thus the
simplest form of ventilation. Such arrangements can, of
course, be applied only where there is a difference between
the inside temperature and that outside — whether the air
inside is warmer or cooler than that outside. But where
fuel must be used solely for obtaining movement of air, it
can be applied more economically in the propulsion of air
by mechanical means.
Propulsion of the air by means of fans or of pumps may
be used either to force the air into a room, or to extract it
from a room.
Theoretically, the propulsion of air into a room would expel
all the foul air through the cracks of windows and doors, even
if no special apertures were made for its removal, and the
existence of pressure in the room would tend to prevent
draughts of cold air from doors and windows ; but in practice,
in the ventilation of hospital wards, the system of propulsion,
i.e. forcing the fresh air into the room, and allowing the
vitiated air to find its way out, has not been generally found
successful as a means of purifying the air. The air forced in
seems to seek the first place of escape, and unless the system
is combined with an efficient system of extraction, much of
the vitiated air will remain in corners and dead angles. It is
therefore advisable always to combine with a system of pro-
pulsion for the inflowing air some method of extraction of
vitiated air. Where the circumstances allow of it, it will be
found simpler to dispense with propulsion, and to rely upon
the action of extraction-shafts to draw in the air required
through adequate channels provided for the ingress of fresh
air. In cases, however, where a large volume of air is required
to be passed continuously into a confined space, and the
channels are limited in size, it may be found advisable to
assist the movement of the inflowing air by propulsion.
The compression of the air caused by propulsion raises the
72 Movement of Air.
temperature of the inflowing air. Some experiments of
General Morin showed that in a system of ventilation where
the pumping in of the air gave a pressure equivalent to %
inches of water, the temperature was raised from 20° to ^5°
Fahrenheit, between the temperature at the place from which
the air was drawn into the fan and the temperature at the
inlet into the room.
The system of extraction by fans is of the highest value in
cases where it is desired to remove particular impurities with
great rapidity ; such, for instance, as in workshops where the
dust of cotton, steel filings, or injurious emanations produced
locally are sought to be removed at once.
The friction of air varies as the square of the velocity multi-
plied by the pressure against the sides of the passage. This
pressure being uniform, its total amount depends upon the
total surface ; that is, the length multiplied by the perimeter
of the cross section. The force required to propel air through
any passage is therefore equal to the square of the velocity
into the total surface multiplied by the coefficient of friction.
It is more convenient to state the force in lbs. per square inch,
or per square foot, or as so many inches of water pressure.
The best form of the formula for practical purposes of
ventilation seems to be —
^ KV^PL
H^—^ '
where
i7= head of pressure in feet of air of same density as the
flowing air ;
L = length of the pipe or passage in feet ;
P = perimeter of cross section in feet ;
A = area of pipe or passage in square feet ;
V = velocity taken in thousands of feet per minute ;
K = coefficient of friction = 0-03 ; but this varies accord-
ing to the nature of the sides of the passage.
This formula is perfectly general, and may be used for any
Movement of Air. 73
fluid ; H always being the head, stated in feet, of the flowing
fluid.
The weight of i foot of air, under the pressure of one
atmosphere, at 32^° Fahrenheit, is equivalent to 0*0807 lbs.
per square foot. The weight of i inch of water at 39°* i
Fahrenheit equals 5'2 lbs. per square foot ; therefore i foot
of air, at '>/f Fahrenheit, under the pressure of one atmo-
sphere, exerts a pressure equivalent to 0*0154 inches of water.
For circular passages, taking D for the diameter, the for-
mula becomes —
H^KV^x
D
These formulae are only applicable to passages whose
diameter is small in proportion to their length. For short
passages the actual length should be increased, for purposes
of calculation, by about 50 diameters of the passage : thus the
formula for short circular passages becomes
for short irregular-shaped passages,
A
It is beyond the limits of this treatise to enter into the
question of the form of propeller which should be used. It
may however be observed, that the best fans have produced
from 70 to 75 per cent, of useful effect in proportion to the
power employed.
There is a third system, which can only be applied in special
cases — ^viz. that of ventilation by means of compressed air,
adopted in the Mont Cenis and St. Gothard tunnels during
construction. The compressed air, after having been utilised
to work the boring machines, escaped into the tunnel, and
provided fresh air for ventilation.
Compressed air has also been applied to produce a current,
74 Movement of Air.
and thus to extract vitiated air, somewhat on the principle of
the steam jet which causes the draught in a locomotive
chimney, but acting by its momentum only.
H M — the volume ;
V = the velocity of the air injected into the channel ;
M^ = the volume of the additional air drawn into the
channel by the movement of the injected air ;
M + M^ = J/i=the total volume of air passing along
the channel ;
Fi = mean velocity of the air, as it flows along the
channel ;
MV^{M ^M^) Fi = M^V^.
If d = density of injected air ;
D = density of air in channel ;
s = section of orifice of injector ;
6* = section of orifice of channel ;
M = and M^ = •
g S
The system was used for the ventilation of some of the
galleries of the Exhibition at Paris in 1867, and was subjected
to experiment by General Morin ; and he shows that the use-
ful effect varies inversely with the cube of the velocity of the
air in the injector.
In a channel having a diameter of about 8 feet, with a jet
of injection of about 5 inches diameter, the velocity in the
channel being from 6 to 9 feet per second, and the velocity of
the jet of injection about %%o feet per second, the useful effect
of the jet only equalled ^V of the power of the jet ; and as
the jet only utilised half the useful effect of the engine, the
general result was to utilise only ^V of the motive power
expended. Therefore this method of propelling air is not
advantageous; but it may be resorted to in special cases
where difficulties exist in applying other methods of pro-
pulsion.
(
^
Movement of Air. 75
There remains the method of extraction by the movement
of the atmosphere alone. If an open tube or shaft be carried
up from a room or enclosed space to a point above, where the
top is exposed to the free movement of the atmosphere, an
upward current will prevail in the shaft so long as there is a
movement in the atmosphere. The movement is of course
unequal in its action. It is powerful when the wind is high.
In calm weather it is very small; but in this country, as
already mentioned, the average velocity of the atmosphere is
above 17 feet per second, and it is rarely quite at rest.
It is very difficult to measure the relation which the current
in a tube or shaft caused by this method of extraction bears
to the velocity of the wind, because there are so many conflict-
ing elements to be considered. The formulae for calculating
the velocity of wind in some of the standard anemometers
are not entirely satisfactory for the very low velocities. The
action of wind, whilst it tends to exhaust the air through the
tube, is, at the same time, acting on all other openings in the
building, either to exhaust or to force in air. Hence gusts of
wind will sometimes cause a reverse action in the tube, in
consequence of some other opening acting temporarily as a
means of extraction.
The temperature inside and outside must also be considered.
If the atmosphere should be without perceptible movement
in cold weather, when the temperature indoors is maintained
for comfort above that out of doors, the difference of tempera-
ture will cause an upward movement in the shaft. In hot
weather, if the shaft is colder than the outer air, a down
current may ensue ; but if, in hot weather, there should be
little or no movement in the shaft, this occurs at a time when
the windows can be kept open, and the air be renewed by
this means.
The friction in the shaft varies inversely with the area ; and
with small tubes it forms a very perceptible element of re-
tardation. Experiments made with tubes three inches in
76 Movement of Air.
diameter tend to show that the velocity obtained in the tube
was about \ of that of the wind ; larger diameters, on the
other hand, produce better results.
These results were obtained in a place supplied, as far as
possible, with fresh air to replace that removed, in a manner
independent of the movement of the atmosphere, and with
the top of the tube freely exposed on all sides.
In consequence of the numerous causes of disturbance
enumerated above, this method of extraction, when applied
to a house, could not be relied on to act on all occasions with
certainty as an extraction-shaft. But it can be relied on to
ensure in one way or other, and to a certain extent, a continual
change of air.
A tube or shaft with an open top acts best. It is, however,
necessary to protect the top, to prevent rain from entering the
tube ; but a cover tends more or less, according to its shape,
to delay the current in the tube or shaft. A 1cowl with a
curved head, arranged to move round with the wind, so as
always to present its back to the wind, would appear to be
the form of covered top best adapted to facilitating extraction,
especially if gradually enlarged at its mouth into an oval
shape, with an aperture somewhat larger than the tube.
CHAPTER VIII.
PRELIMINARY CONSIDERATIONS UPON THE INFLOW
AND REMOVAL OF AIR.
The efficient ventilatioa of a building depends upon the
efficient ventilation of each room in that building. The first
matter for consideration therefore is the manner in which the
ventilation of a room can be best secured.
The most efficient way of thoroughly renewing the air of a
room is by means of open windows and doors, when these are
so placed as to ensure a thorough draught ; and open windows
should always be resorted to when the weather permits.
But the windows cannot always be kept open. In cold
climates the windows must be closed to keep the rooms warm.
In hot climates the windows must be kept closed to keep the
rooms cool. In the one case warmed air, in the other cooled
air, should be admitted independently of the windows. More-
over, windows are so placed in a room as to meet the require-
ments of light, and do not therefore necessarily occupy the
most advantageous position for the continuous admission of
air. Therefore every room should have special arrangements
for the admission and extraction of air. This entails inlets
and outlets, and in some cases ducts and flues leading thereto.
The rate and temperature at which air is removed and
admitted materially affects the comfort of the occupants of a
room.
78 Preliminary Considerations upon
The velocity of the air as it flows in and out of a room, as
measured at the openings for admission or exit, should not
exceed i foot, or at most % feet, per second ; firstly, in order to
prevent a sensible draught being felt ; and secondly, because
a low velocity is favourable to the uniform diffusion of the
incoming air through the room.
To avoid friction, it is convenient that the velocity in the
channels leading to the main extracting shafts should not
exceed from 3 feet to 4i feet per second, and the velocity
in the main extracting shafts themselves should not exceed
from 6 to 7 feet per second.
This latter velocity will, under general circumstances, and
where the extraction is effected by means of a heated shaft,
be provided by a difference of temperature between the inside
and outside of from 30° to '>^^ Fahr. In special cases, on
grounds of construction or otherwise, it may be found neces-
sary to exceed this.
These velocities would be regulated by the size given to
the inlets, outlets, supply channels, and extracting shafts, as
compared with each other respectively, and with the quantity
of air to be supplied and removed; which quantity would
depend upon the number of occupants of the rooms to be
provided for, and the amount of air to be allotted to each ;
on the conditions required for the ventilation of corridors,
lobbies, staircases, water-closets, and other subsidiary accom-
modation ; and on any other conditions necessary to be
adopted in fixing the supply. The areas thus obtained should
be the free areas, exclusive of gratings or other impediments.
Air should be introduced and removed at such parts of the
room as not to cause a sensible draught. Air flowing against
the body, at or even somewhat above the temperature of the
air of a room, will cause an inconvenient draught ; from the
fact that as it removes the moisture of the body, it causes
evaporation or a sensation of cold.
Air should not as a rule be introduced near the floor level.
the Inflow and Removal of Air. 79
The openings would be liable to be fouled with sweepings and
dirt. The air, unless very much above the temperature of the
air of the room, would produce a sensation of cold to the
feet.
The orifices at which air is admitted should be above the
level of the heads of persons occupying the room ; the current
of inflowing air should be directed towards the ceiling, and
should be as much subdivided as possible by means of
numerous orifices.
Air admitted near the ceiling very soon ceases to exist as
a distinct current ; and will be found at a very short distance
from the inlet to have mingled with the general mass of the
air, and to have attained the temperature of the room, partly
owing to the mass of warmer air in the room with which the
inflowing current mingles, partly to the action of gravity,
where the inflowing air is colder than the air in the room ;
and where there are open fireplaces, the result is acce-»
lerated by the action of the fire.
The ventilation of rooms is affected by their situation. In
a house with a central staircase carried from the ground floor
to a lantern light in the roof, when the air in it is warmer
than the outside air, it becomes a powerful shaft ; and being
of such a large size, tends to draw in the air from adjacent
rooms, and even down the chimneys, especially when the
chimney is cold, or when its size is greater than required for
the removal of the air provided for its supply. In the latter
case, a double current, one up, one down, and both sluggish, is
sometimes established in the chimney.
A smoky chimney will therefore often be cured by being
reduced in area, so as to reduce the volume of air required to
fill it, or by an adequate provision of fresh air to the room in
which it is placed, or by a supply of air in an adjacent hall or
staircase.
The effect of a high wind is to diminish the air-pressure in
a house when all windows are closed on the side of the outer
8o Preliminary Considerations upon
air-pressure : hence although some of the chimneys may have
an accelerated draught due to the velocity of the wind, the
action of the air-pressure may be to cause other of the
chimneys to smoke, the remedy for which would be to open
slightly the windows on the side of the air-pressure, so as to allow
the pressure to act equally through the house. It will fre-
quently happen that the open fires in the rooms which require
to be fed with fresh air, and the warm air shaft of the central
staircase, will combine to draw in the air from every available
opening. They will draw up the air from the basement ; they
will draw it, if they can, from the water-closet and sink-pipes,
unless the water-closets and sinks are in projecting buildings
cut off by lobbies ventilated from the open air.
For these reasons it is of importance not only to shut off
the staircase from the basement, but to provide fresh air to
the staircase ; and when open fires are used, to supply each
room in which there is an open fire-place with its own supply
of fresh air. If the temperature of the room is to be kept
up to a pleasant heat, this must to some extent be warmed
air.
In a building with halls and passages, the inflow of cold air
through the doors when opened must be guarded against by
the independent supply of fresh air to, and the extraction of
vitiated air from, all parts of the building, and by the main-
tenance of a proper temperature in all parts. By this means
draughts occasioned from opening doors would be avoided.
An inflow of cold air occurs only where the ventilation and
warming are defectively arranged.
The fresh air should be obtained from places where there
are no adjacent sources of impurity ; especially not from the
vicinity of ash-pits, manure-heaps, gully-gratings, or other
sources of foul air. The inlets from the outer air should be at
least two feet from the ground, and the surface near should be
paved and sloped away from the inlet, so as to carry off wet
rapidly. It has been estimated that the impurities of town
the Inflow and Removul of Air. $>\
air are very much diminished at ioo yards height, And ife not
found above 600 yards in height — a London fog will rarely be
perceptible at a height of above 100 yards— coniSequently to
bring pure air into a large town the simplest way would be to
draw it down from a height by means of a high shaft or tower.
The Houses of Parliament could be supplied with very much
purer air than is now provided for them by bringing the air
from the top of the Victoria Tower.
The temperature at which air should be delivered in a room
depends somewhat on the temperature of the outer ain With
a temperature out of doors of 86\ air delivered at 60^ would
be felt as too cold. Similarly, in the arctic expedition, with
an out-of-doors temperature —40° below zero, a temperature
of -f 40° was felt to be hot.
In this climate the temperature indoors should be main-
tained at from 58^ to 66°, and the warmed inflowing air
should be supplied at a temperature a few degrees above this,
but as nearly as possible not to exceed from 68° to 75°, or at
most 80°. The hygrometric condition of the air must also be
considered. If the air is too dry, it may, after it has been
warmed, be passed over vessels containing water, to allow it
to take up additional moisture — but the natural dampness of
an English climate renders this less necessary here than it
may be elsewhere. It has not unfrequently happened that
complaints of the oppressiveness of dry air artificially warmed
have been caused rather by the insufficiency of the supply of
warmed air than from its dry condition.
The channels for the admission of air should, as a rule, be
short, direct, and accessible.
Long channels collect dirt, and form a refuge for insects.
But if it is necessary to make them long, they should be easily
accessible for cleaning. Deep underground channels and
receptacles will modify materially the temperature of the
inflowing air, because in winter the temperature of the earth
within a short distance of the surface is warmer, and in
G
82
Preliminary Considerations upon
summer it is cooler than that of the air ; channels for the
purpose hi utilising this effect of temperature should be of a
rectangular shape, so as to afford a lai^e surface in propor-
tion to their area ; and they should be of a good conducting
material.
Underground channels should always be impervious to
ground air ; and, as has been already shown, there are very
few materials impervious to air.
The liability of air in underground channels to mix with
ground air would be diminished if the air were supplied to the
channels or receptacles by propulsion, and retained in them
under some pressure.
Undei^round channels should be perfectly dry. Damp
channels overcharge the air with moisture ; and thus they
interfere with the warming of the air ; they induce the pre-
sence of animal and v^etable life, which dies and decays,
and renders the air impure.
In towns where the atmosphere is fuU of particles of soot
and other impurities, the inflowing air deposits these particles,
and rapidly blackens any surfaces it impinges on. The im-
purities may be removed by passing the air through a filter
made of cotton wool laid lightly, to a thickness of about half
an inch, on a copper wire frame. (See Figs. 7 and 8.)
The cotton wool must be renewed at intervals, dependent on
ike Inflow and Removal of Air. 83
the state of the atmosphere. In London fogs it should not be
left on for more than a few days. In clear weather in London
it will last two or three weeks.
Sliced sponge acts equally as an air filter, and may be easily
washed, dried and replaced.
A system has been introduced of endeavouring to remove
impurities from the inflowing air by causing the current to
come in contact with a surface of water. In damp weather
this is liable to the inconvenience that the water keeps up the
saturation of the air with moisture. In dry hot weather the
system which has recently been adopted for washing smoke
by passing it through a chamber filled with spray, might be
adapted for washing the impure air of towns.
Extraction-shafts, when for ventilation only, should be
placed so as not to occasion unpleasant draughts ; but their
position must depend also upon other conditions, wkich will be
further alluded to ; meanwhile it may be observed that it is
advisable that as far as possible extraction-shafts from dif-
ferent rooms, the operation of which depends on temperature,
should be independent of each other. Where the rate of
extraction is sluggish, and the temperature is low in the shaft,
there may arise conditions in one room whicli may determine
a reverse current, and then, when there is not a complete
separation, the bad air from one room may be introduced into
another room. And even when the flow of air into an
extraction-shaft has been rapid througli the outlets from all
the rooms communicating with it, smells from one room
have been diffused into other rooms along the line of the
extraction-shaft.
Extraction-flues in which the temperature exceeds that of
the outer air should be arranged whenever possible to con-
duct the air upwards, so as to assist its flow. Every descent
in the flue has to be compensated for in some way, either by
extra height of shaft, temperature, or expenditure of force.
Thus in a chimney-flue, where the extraction depends upon
G %
84 . Inflow and Removal of Air^
the heat in the flue if a portion of the flue near the fire is
horizontal, it is found in practice that the flue cannot be
depended on to act efficiently unless the vertical height is
double the horizontal length.
The best form for an extraction-flue is the circular form,
because it affbrds a maximum of area with a minimum of
perimeter, or surface, and therefore causes a minimum of
friction.
The various considerations enumerated above apply equally
whatever be the manner in which the air is admitted or
removed.
It should, however, be accepted as an axiom, that by the
best ventilating arrangements we can only obtain in our rooms
air of a certain standard of impurity ; and that ventilating
arrangements are only makeshifts to assist in remedying the
evils to which we are exposed from the necessity of obtaining
an atmosphere in our houses different in temperature from
that of the outer air. To obtain that temperature we sacrifice
purity of air ; therefore, whenever the outer temperature
permits it, windows should be widely opened, so as to replace
the air of the room by fresh air, as often as possible.
CHAPTER IX.
SIMPLE VENTILATION WITHOUT WARMED AlR.
The simplest way of obtaining a change of air in a room
is to take advantage of the movement in the air produced by
a change of temperature, or by the action of the winds.
Wherever there is an outlet and an inlet for air in a room,
this system will operate. The open fireplace is one example
of it ; the sun burner is another example, but the system is
also applied in every room in which there is an opening at
the upper part, out of which the warmed air can pass, and an
opening either level with it or below it, through which fresh
air can flow in.
Thus an ordinary sash window is the simplest example.
If the top sash is lowered and the bottom sash raised, the
warmed air passes out of the room at the top, and the cooler
outer air flows in below. Hence, for an inlet for air to an
ordinary room, provided with a fireplace, but unprovided
with special inlets, a very simple plan is to cut a slit above
the lower bar of the upper sash of a window, so as to leave a
clear space of about a quarter of an inch along its whole length,
through which the fresh air will be drawn in in an upward
direction.
Ventilators which act similarly to direct the current of air
towards the ceiling are sometimes introduced into the upper
panes of window-frames, such as hopper ventilators, or
86
Simple Ventilation
Moore's louvred panes, but these are all makeshifts. Every
room should have special inlets and outlets for air, arranged
so as to be independent of the windows ; although the win-
dows, when they can be kept open, are the best means for
the renewal of the air in a room.
The relative position and arrangement of the inlets and
outlets regulate both the comfort and efficiency of the venti-
lation.
It is therefore necessary to consider what currents are
caused in a room by ventilating openings.
In the first place, the question should be considered apart
from an open fireplace, and apart from the question of
warming the inflowing air.
If a room has two outer walls on opposite sides, and if an
opening be made in each wall, and if the wind blows against
one of the walls, there will be an increase of pressure against
that wall, and a diminution of pressure against the wall
opposite ; consequently air will be forced in through the inlet
on the side against which the wind blows, and be extracted
on the other side.
Hollow ventilating beam.
I " n II n H II II 11 H I
5
\ ^
Fig. 9.
Fig. 10.
Barrack-rooms have been occasionally ventilated by hollow
beams, carried across the rooms from one outside wall to the
other, communicating with the open air at both ends, and
without Warmed Air. 87
also provided with openings into the room, but having a
wooden partition placed across in the centre of the beam, so
as to compel it to act both as an inlet and an outlet when the
wind is blowing against either outer wall, as in Fig, 9.
The action becomes more efficient if the beam be dispensed
with, and the openings in the opposite walls retained. The
most convenient form for such openings is the Sherringham
ventilator; Figs. 10, 11.
Fig. I
Tills consists of an iron air-brick or box inserted close to
the ceiling of the room, and affording a direct communication
with the external air. In order to prevent the air from
coming in by stray currents, there is placed at the mouth of
the opening within the room a hopper-shaped valve, hinged
at its lower side and opening towards the ceiling ; the result
of which arrangement is, that the inflowing current is thrown
up towards the ceiling, and difTused to a greater or less extent
in the general mass of air within the room.
This ventilator may, under certain conditions, act as an
outlet ; but when the room is shut up, it would, especially
with a fire in the grate, act as an inlet for fresh air.
Considered as an inlet, its principle and position are both
good, but acting by itself It is not a sufficient ventilator for
rooms with a large number of occupants.
Inlets have been formed by vertical tubes, the opening to.
8a
Simple Ventilation
I
r\
i
I
i
the outer- air being made near the floor, and the tube being
employed as a means of carrying the point at which the air is
allowed to enter the room to a height of 5 or 6 feet or more
above the floor. This is convenient in cases where necessities
of construction make it desirable to place the opening to the
outer air low down as compared with the point of entrance of
the air into the room. The tube has the advantage of directing
the inflowing current upwards towards the ceiling — but in con-
sequence of the friction of the sides of the tube the velocity
with which the air enters the room is less than it would be if
it came in through a shorter channel
and a more direct inlet inclined up-
wards like a Sherringham ventilator.
The main objection to these tubes
is that they form very convenient
receptacles for dirt, insects, cobwebs,
and dust, which after a time may
injuriously afi*ect the air passing
through them. Moreover, inlets of
this shape do not readily lend them-
selves to act the part of outlets when
occasion requires, which is so con-
venient a feature of the Sherringham ventilator. Upon
the whole Sherringham's is the most convenient form, and it
IS easily cleaned.
Where a room has two outside walls, and is provided with
openings on both sides, this inflow and outflow of air is
almost certain to go on continuously, in consequence of the
movement of the outer air.
Where rooms have only one outer wall, other conditions
prevail. The Sherringham ventilator, in such cases, would
be found to act on occasions both as an outlet and an inlet ;
but its action would not be sufficiently energetic, consequently
an additional outlet becomes necessary. This is best pro-
vided by means of a vertical shaft or tube carried from near
i
Fig. i».
1
without Warmed Air. 89^
the ceiling to above the roof. In a room possessing a
chimney-shaft, and with few occupants, an Arnott's ventilator
is convenient; its main use being to assist ventilation on
those occasions where the fire is low or not lighted. The
merits which Dr. Arnott's chimney-valve possesses have led
to its extensive introduction into barracks, hospitals, private
houses, &c. It consists of an oblong metal frame inserted
into the room chimney near the ceiling. Its object is to take
advantage of the upward draught of the chimney in drawing
the upper strata of the air of the room through the frame into
the flue, while to prevent down-draughts of smoke into the
room, a light silk or talc flap-valve, supported behind a
perforated metal plate, is placed in the opening of the box
into the room. This valve, like every other, requires certain
conditions for its action. If the throat of the chimney be
very wide, the quantity of air and smoke which pass up the
shaft from below will be more than the chimney can accom-
modate at its narrowest part, where the ventilator is placed,
and smoke will consequently pass through the valve into the
room. Wherever, therefore, Arnott's valve is to be used, the
throat of the chimney between the fireplace and the valve
must be contracted to such an extent as to leave a balance in
the draught to be supplied by air passing through the valve.
As, however, the amount of this balance — in other words,
the number of cubic feet of air which can pass through the
valve into the chimney per hour — is very limited, this form of
ventilator is not adapted to be the only outlet for a barrack-
room, dr for any room with several people in it.
Under such circumstances, as well as in rooms where this
is not available, an outlet should be provided by • a shaft
carried from near the ceiling to above the roof. (Fig. 13.)
The velocity in these shafts, when acting freely of them-
selves, is dependent of course on the diff'erence of temperature
between the air in the room and the air without, on the
amount of movement in the outer atmosphere, on the adequate
90
Simple Ventilatio7i
Fig. 13.
supply of fresh air in place of that removed, and on other cir-
cumstances. When the temperature is nearly equal, as, for
instance, when the windows are
open, there is very little upward
draught, except as the result of
movements in the atmosphere with-
out, but when the windows are
open the room is being ventilated
without the shaft. At other times a
current varying from 2 J to 5 feet
per second may be relied on, and
often a stronger current will be found
to prevail.
It sometimes happens, especially
in rooms with a very short shaft,
as, for instance, rooms near the roof,
that from the action of the wind
the current becomes irregular, and is
occasionally reversed, and produces down-draughts — so that
the shaft becomes temporarily an inlet, and the Sherringham
ventilator an outlet
A reverse current in the shaft may be occasioned also if
there is a large open fire in the room inadequately supplied
with fresh air; or if a large and lofty hall or staircase is in
proximity to the room — these may act like large shafts to
draw in the air from the room and down the ventilating
shafts.
Such an effect equally provides the room with fresh air;
but to prevent inconvenience to the occupants, it is advisable
to terminate the shaft a little below the ceiling with a solid
bottom and with side openings covered by inverted louvres, so
that any down current would be directed towards the ceiling.
The sizes which were adopted for outlets and inlets of
this description in the case of barrack-rooms are, for shafts
or tubes in rooms next the roof, a sectional area of one inch
without Warmed Air, 91
to every 50 cubic feet of room-space; for the floors next
below the upper floor a sectional area of one inch to 55 cubic
feet of room-space ; and, where the barrack consists of three
floors, for the lower floors a sectional area of one inch to
60 cubic feet of room-space. For inlets one square inch for
every 60 cubic feet of content of the room as the clear inlet
area exclusive of gratings. This is the opening to the outer
air — the opening into the room should afford an area larger
than this, so as to reduce the velocity of the inflowing current.
As the velocity of outflow and consequent inflow depends
on temperature, provision must be made for closing either
wholly or partially the inlets in cold weather; and it is
assumed that in very mild weather the sluggishness of the
ventilation would be assisted by opening the windows. In
barrack-rooms, whatever be the weather, the windows are
opened during a certain time every day. These sizes were
adopted on the basis; of the cubic space allotted being 600
cubic feet per man, and that a volume of fresh air not less
than 1200 cubic feet per occupant per hour should be
admitted. The contamination of the air varies with the
number of occupants. In hospital wards, in which the volume
of air to be removed per occupant is greater than in barracks,
the same sizes were still adopted ; because in hospitals, the
cubic space per occupant being much greater, the change of
air per occupant would be correspondingly greater. But in
places where the cubic space is much less than this, such as
in some schools, workhouse dormitories or in common lodging-
houses, a larger proportional area to cubic space may be
found advisable.
There are forms of shafts which have been devised to act
both as inlets and outlets, but in order to do so they require
fixed conditions. Alter these fixed conditions and any of
them may become wholly outlet or wholly inlet. The con-
dition essential to their operation is, that the room to which
they are applied be closed, and in a closed room their action
92
Simple Ventilation
is singular^ If a number of people be crowded into a room
with the fireplace closed and the doors and windows shut, and
if a tube of an apparently sufficient area to afford ventilation
for the inmates be carried from the ceiling of the room above
the roof of the building, there will be an irregular effort at
effecting an interchange between the air of the room and the
outside air. The outer air will descend, and the inner air will
ascend, in fitful, variable, irregular currents, and the room will
be badly ventilated, if ventilated at all.
i«»S^?^{««S5»««5»?iS»4?S
^
:i^«ssssss!ss^!«^;si4;s^^
Fig. 14.
l^ig- 15-
But singularly enough, no sooner is the tube divided longi-
tudinally from top to bottom by means of any division,
however thin, than its action becomes immediately changed —
a current of air descends into the room continuously on one
side of the partition, and a current of foul air ascends from the
room continuously on the other side of the partition. One
half of the tube supplies fresh air to the inmates of the room,
and the other half removes foul air, so that if the size be
properly adjusted the air in the room is kept sweet. (Fig. 14.)
Watson's Ventilator (Fig. 15) supplies this principle in its
elenuentary form. It consists of a square tube with a division
without Warmed Air.
93
down the centre, one side affording a tube slightly higher than
the other : it has no means of diffusing the descending current.
Mackinnel's ventilator (Fig. i6) professes to be an improved
application of the same principle. It consists of two tubes,
one within the otherj leaving a space between them. The
inner tube is the longer, and projects above the outer tube at
its upper end ; .the inner tube also projects a little below the
"^
^^^^^^^^
o
r
?%5ii»i4Sa%K55»}N^J5«N«
Fig. 1 6. Fig. 17.
opening of the outer tube in the ceiling, to give support to a
circular flange projecting parallel with the ceiling, and con-
cealing the opening of the outer tube. The action of this
contrivance is as follows: — The greater length of the inner
tube determines the upward current to take place in it ; it
therefore becomes the foul air shaft. The outer tube becomes
the fresh air inlet, and the descending current striking against
the flange, is thrown out in the plane of the ceiling, and so
diffused.
Muir's ventilator (Fig. 17) consists of a square tube, like
94 Simple Ventilation without Warmed Air.
Watson's, divided into four parts, A^ A, B, By by partitions, in-
serted diagonally. These partitions are carried above the top
of the tube, and the box is completed outside and above the
roof by louvres instead of solid sides. The object of this
arrangement of divisions and louvres is to secure not only up-
ward and downward currents at ordinary times, but to take
advantage of any movement of the external air, light, winds,
&c., which, by striking through the louvres on any angle, would
cause a stream of air to be projected down into the room, and
would assist the extraction of the air on the side away from
the wind.
All these ventilators act as desired in a closed room, but as
soon as a door or window is opened they become simply
upcast shafts ; they cease to supply air, and the air supply
comes in from the other openings. Again, if there be a fire-
place in the room, with a strong fire in it, and the doors and
windows shut, the fire will supply itself from these ventilators,
and they will become inlets.
It is obvious that these plans possess certain advantages in
cases where they are applicable. In single rooms standing
apart, such as churches, chapels, schools, libraries, &c., warmed
by stoves or hot water pipes, and where the doors are kept shut
for hours at a time, any of them will answer as ventilators.
In stables, also, of a certain construction, they will be more
or less applicable.
In the case of living-rooms in houses they would not be
applicable, both on account of the difficulty and cost of intro-
ducing the apparatus into a number of detached rooms on dif-
ferent floors, and on account of the existence of open fireplaces.
Inlets and outlets may be varied in form, but those men-
tioned are amongst the simplest forms. It must be borne in
mind that so long as efficient action without draughts can be
obtained, the best form to adopt is that which is simplest and
most easily cleaned.
CHAPTER X.
OBSERVATIONS ON WARMING.
It will have been apparent in the preceding chapters that
the question of ventilation cannot be separated from that of
the temperature of air. In a cold climate the air required to
replace vitiated air must be warmed. In a hot climate cool
air must be supplied. The question must be considered in
the aspects of health, comfort, and economy.
Comfort and health are practically synonymous ; and for
these purposes in this climate the day-temperature of a room
should be maintained at something between 58° and 66°. The
night-temperature should not be so high, but it is not desirable
that the night-temperature should fall below 40°. It should,
however, be noted, that with a high temperature the quantity
of oxygen present in the air is diminished. Thus, a cubic foot
of dry air at 3^° weighs 566*85 grains, and if the proportion of
nitrogen and oxygen be assumed to be by weight 77 and 23
per cent., and the slight amount of carbonic acid be neglected,
there will be in a cubic foot —
436*475 grains of nitrogen.
130-375 » oxygen.
566.850
As a man draws, on an average, when tranquil, 16.6 cubic
feet per hour into his lungs, he will thus receive 130-375 x i6-6
= 2164-2 grains of oxygen per hour.
96
Observations ofi Warming.
At a temperature of 80° the foot of air weighs 5 1^*3^ grains,
and is made up by weight of —
397.61 grains of nitrogen,
118.77 „ oxygen,
516.38
Therefore, in an hour, if a man withdraws 16-6 cubic feet,
he will receive 118.77x16.6=1971.6 grains of oxygen per
hour. Or, in other words, in an hour he would receive
192.6 grains of oxygen less with the higher temperature;
that is to say, he would inhale an amount of oxygen equal
to about 90 per cent, of the amount he would breathe at the
lower temperature.
If saturated with moisture, a cubic foot of air will contain
130 grains of oxygen at 32°, and iia grains at 100°.
The application of heat in an economical manner requires a
consideration of the conditions under which heat is generated
and diffused.
The standard unit of heat is the amount required to raise
one pound avoirdupois of water at 32° one degree Fahrenheit.
The specific heat of a body is the number of units of heat
necessary to raise that body 1° Fahrenheit. The number of
units of heat necessary to raise the temperature of one pound
avoirdupois of the following bodies 1° Fahrenheit is —
Air
Unit of heat,
constant volume . . .169
constant pressure . . .238
Water at 32° loo
Pine- wood -65
Oak .57
Ice -50
Olive oil .31
Unit of heat.
Marble and Chalk .... •21
Glass , •19
Cast iron .13
Wrought iron -ii
Copper .09
Lead .03
It takes 966*1 British units of heat to evaporate ilb. of
water under one atmosphere.
In order to find the quantity of heat required to produce a
given rise of temperature in a given weight of a given sub-
Observations on Warming. 97
stance, it is necessary to multiply together the rise of temper-
ature, the weight, and the specific heat of the substance.
But the specific heat of bodies is somewhat greater at high
temperatures than at low temperatures. Thus if the specific
heat of water at 32° be taken as i, its specific heat at 446°
Fahrenheit will be i«o5. i lb. of air at 31^° contains i(Z-38 cubic
feet, and i cubic foot of air at 32° weighs 'oS lbs. At 6:z° its
volume would be increased to 1-061, and its weight would be
•076 lbs., whilst at 104° the volume would be i«i46 and the
weight -07 lbs., and at 212° the volume would be 1*365 and the
weight -059 lbs. All gases, dry air, and vapours out of contact
with their generating fluids, expand very nearly alike, and the
following formula is a fair expression of the rule of expansion —
458.4+ r
in which M=z volume of gas or air, at temperature J", and m =
volume of air at new temperature t.
The rate of expansion increases slightly with the pressure.
When the pressure is not constant, the volume of any gas
varies in the inverse ratio of the pressure — the temperature
remaining nearly constant. The pressure is the total pressure
above a vacuum. Thus one cubic foot of air has the pressure
of the atmosphere of 14.7, or say about 15 lbs., per square inch
upon it to begin with, and thus its volume at an additional
I X 15
pressure P above atmospheric pressure would be — p •
Where there is a change both in temperature and pressure,
and P = pressure corresponding to temperature T and to
volume Jf, and p = pressure corresponding to temperature t
and volume m^ the rule becomes —
-_ P 458-4+/
m=Mx — X *^
/ 458-4+^
When water is present the rule becomes
H
98
Observations on Warming.
in which J/, P^ 7", and F are the volume, pressure, tempera-
ture, and elastic force of vapour corresponding to each other
in one case, and w, /, /, / in the other case.
The following table shows approximately the cold produced
by dilation and the heat produced by compression of air. The
volume at atmospheric pressure at the sea level and at 60®
Fahrenheit being i«o.
Atmospheres.
No. of Inches
of Mercury.
Volume of
the Air.
Actual Temperature
of the Air
during the process.
(Fahrenheit.)
Difference due
to compression
or expansion.
(Fahrenheit.)
0-5
15
1.634
- 36°
-96°
0.83
as
IT37
+ 33°
- »7°
lOOO
30
1.000
+ 60°
0°
1-25
37-5
0.85
+ 94°
+ 34°
1-5
45
0.75
+ 124°
+ 64'
2.0
60
0*61
t-i76°
+ 115°
Thus if air at a temperature of 60** be compressed to half
its volume, or to a pressure of two atmospheres, its temperature
is raised to 175° Fahrenheit. If, on the other hand, it be
expanded so as to occupy double the space, the temperature
would be decreased to nearly 36° Fahrenheit below zero ; and
hence if air be compressed, and if the compressed air be
allowed to cool down to the temperature of normal air, and
the air be then allowed to expand, a degree of cold will be pro-
duced equal to the difference between that caused by the com-
pression and the normal temperature. This affords an efficient
means of supplying cooled air for ventilating purposes.
The heating power of different kinds of fuel varies consider-
ably, depending chiefly upon the proportion of carbon and
hydrogen which they contain. One atom or i3«5 lbs. of
hydrogen combines with one atom or 100 lbs. of oxygen to
form ii2'5 lbs. of water. The heat evolved by this com-
bination is (^%^^'>i^ units per pound of hydrogen. One atom or
75 lbs. of carbon unites with % atoms or !200 lbs. of oxygen to
form :&75 lbs. of carbonic acid. The heat evolved in this
Observations on Warming. 99
process, according to Dulong's experiments, is 12,906 units
per lb. of carbon. One atom or 75 lbs. of carbon combining
with one atom or 100 lbs. of oxygen forms 175 lbs. of carbonic
oxide. The heat evolved in the process, according to Dulong's
experiments, is ^1495 units per lb. of carbon, and, according to
the same experimenter, i lb. of carbon in the form of carbonic
oxide burning to carbonic acid evolves 10,400 units of heat.
If the constituents of fuel be classed under C = carbon,
H = hydrogen, and O = oxygen, and refuse, the theoretical
evaporative power or total heat of combustion in units of
evaporation per unit of weight of fuel from chemical analysis
may be briefly expressed by the formula —
Theoretical evaporative power = 156"+ 64 (//" — ^)
as shown in the following table of examples of theoretical
evaporative powers of fuel.^
Carbon 15
Hydrogen 64
Various hydrocarbons from 20 to 2'i\
Charcoal and coke „ 12 to 14
Coal, best qualities : — anthracite 15
bituminous .... from 14 to 16
oxygenous about 13}
n If
V ,» brown „ la
Peat, absolutely dry , 10
Wood „ „ 7j
The oxygen required for combustion is supplied hy air.
^ The following are the results which have been obtained by direct experiment
by various experimenters of the value of several of the above substances as gene-
rators of heat.
Units of hfeat
per lb. of fuel.
Hydrogen burning to water will give 62,535
Petroleum will give 20,240
Carbon burnt to carbonic acid 12,906 to 14,040
)* » oxide 2,495
Coal (mean of 97 varieties) i3>oo7
Charcoal from wood , 1 2,000
Coke 10,970
Wood, perfectly dry 6,480
Wood, in ordinary state of dryness (i.e. with 20 °/q of water) 5,040
Peat (dried naturally) ; 7,150
Peat (dried artificially) . 8,736
H %
lOO Observations on Warming.
One atom or loo lbs. of oxygen combines with % atoms or 350
lbs. of nitrogen to form 450 lbs. of air, equivalent to about
5800 cubic feet of air at 6jj° Fahrenheit. One pound of hydro-
gen requires for its combustion 8 lbs. of oxygen, equivalent
to 36 lbs. or about 470 cubic feet of air ; and one pound of
carbon requires for its combustion 2*69 lbs. of oxygen, equiva-
lent to 13 lbs. or 157 cubic feet of air at 62° Fahrenheit. The
net weight of air which is chemically necessary for the complete
combustion of a unit of weight of fuel may be expressed by
the formula —
i2C+36(/^--^),
where C stands for carbon, H for hydrogen, O for oxygen.
Nitrogen passes through a fire without material alteration,
and for purposes of combustion the oxygen alone is available.
Experience shows that the air which has passed through a fire
retains a considerable proportion of its normal quantity of
oxygen, and therefore for practical purposes of combustion
the supply of air should be increased beyond the quantity
which theoretical considerations show to be necessary, in the
ratio of li to i or a to i.
According to this view, i lb. of coal or charcoal requires for
its combustion about 300 cubic feet of air at 6a° Fahrenheit ;
I lb. of dry wood requires about 160 cubic feet of air. The
efficiency of a furnace may be diminished by from *% to '5 of
its value through unskilful firing.
In a close stove perfect combustion depends on the area of
the grate, and other apertures for admitting air, with reference
to the fqel used, to the height of chimney or other means for
drawing or propelling the air through the fuel, and to the power
of regulating the inflow of air by dampers or doors. In open
fireplaces, whilst a blazing fire will be best obtained by a
grating under the fire, yet if the air be properly guided to the
back as well as to the front and sides of the upper part of the
fuel in an open fire, a bright fire will be obtained; as for
Observations on Warming. loi
instance, with Dr. Arnott's pain of a closed bottom to the
fireplace. In all cases when the supply of air is insufficient,
carbonic oxide is formed.
When carbonic oxide is in course of formation in an
ordinary grate burning coal, the fact is made known by the
blue-coloured flame sometimes seen. When this occurs it is
an evidence that there is an insufficient supply of oxygen at
that part of the fire for supporting combustion. The small
number of units of heat evolved in the formation of carbonic
oxide shows the wasteful effect of burning coal with an
insufficient supply of air.
The effect of water in a combustible is to diminish the
actual weight available for producing heat, as well as to
absorb such a proportion of the heat generated as may be
necessary for evaporating the water ; therefore fuel should be
as dry as possible. For instance, a fire supplied with damp
wood will give out scarcely any heat.
When oxygen and carbon combine, the volume of carbonic
acid formed is nearly the same as that of the oxygen con-
sumed ; therefore when a combustible contains carbon only,
the volume of gas in the chimney is the same as that of the
air entering the fire expanded to the volume due to the
increased temperature.
The air will be heated to a temperature varying with the
volume of air admitted, and with the heating power of the
fuel. If half the air admitted be consumed, the temperature
of the air as it leaves a coal fire will be 'Xi^^'^ Fahrenheit ; but
if only one quarter of the air were consumed the temperature
would be 1159°. These temperatures are rapidly lost by
radiation, and the temperature in the chimney of a well con-
structed steam boiler is not above S^d^. Nor is it desirable
that a greater temperature should be obtained, because be-
yond that temperature the increase of the volume of air by
expansion limits the discharging power of the chimney.
Thus, assuming a chimney of 32^ feet height, with an outside
102 Observations on Warming.
temperature of 62^ and a temperature of air in the chimney of
192°, the velocity of the expanded hot air at exit is 24-69 feet ;
whilst that of the cold air entering the chimney is 1973 feet
per second.
At a temperature of 582® in the chimney, the velocity of
the expanded hot air at exit would be ^%'(i feet ; whilst that
of the cold air entering the chimney would be 26«3 feet ; and
at 712° in the chimney the velocity of the expanded hot air at
exit would be 58*44 feet per second, but in consequence of the
expansion of the air, the velocity of the cold air entering the
chimney would be only 25-99 ^^^^ P^^ second, and higher
temperatures would show a greater diminution.
Radiant heat passes through moderate thicknesses of air
without sensibly heating the air, so that it may be assumed
that air cannot be heated by the radiant heat from a flame or
an open fire ; but the radiant heat warms the bodies which
intercept the rays, and these bodies warm the air. For mode-
rate temperatures the emission of heat from bodies by radiation
is proportional to the difference of temperature, but for high
temperatures and great differences of temperature, the propor-
tionate emission is much greater. The radiant power of a body
is equal to its absorbing power, and varies with the nature of
the surface. The units of heat emitted or absorbed from a
square foot of surface per hour, for a difference of 1° Fahrenheit
are —
Silver, polished 0265
Lead, sheet -1328
Iron, ordinary sheet •5661
Glass -5948
Cast iron, new -6480
Building stone, Plaster. Wood, Brick . . -7358
Sand, fine '740o
Water 1*0853
Heat is emitted and absorbed in an accelerating ratio in
proportion as the difference of temperature increases between
the body from which the heat is radiated and the body which
receives the heat ; and with the same difference of tempera-
Observations on Warming.
103
ture between the recipient and the radiant, the effect of the
radiant will be greater according to the increased temperature
of the recipient. In. other words, the ratio of the emission of
heat increases with the temperature.
Excess of tem-
perature of the
radiant over that
of the recipient
in degrees
Fahrenheit.
Temperature of recipient of radiant heat
in degrees Fahrenheit.
3^°
50°
104^
212°
18°
108°
324°
Ratio of heat emitted in units of heat.
•997
I-2I2
2 07
1075
1307
2.23
1-355
1.648
2-8l
2*150
3-615
4.46
Mr. Anderson made some experiments in 1875 on hot
water pipes at low temperatures ^, and found that with a con-
stant difference of temperature of 50° Fahrenheit, between
the surface of the pipes and the air —
With the temperature of air =
32°
39°
46°
S3°
60°
The total heat units given )
out by pipes was == \
6887
69*89
70.94
72'OI
73-13
For the several reasons above mentioned, it is more econom-
ical to effect the warming of a given space by means of a highly
heated surface than by a surface emitting a lower temperature.
* The total amount of heat radiated per square foot per hour by heated iron
pipes may be found by the expression my.c? (a*— i), and the heat carried off by
convection or contact vnth air in atmospheric air by the formula —
in which a « 1-0077, ^ — temperature of air surrounding the pipes, / = difference
of temperature between the air and the pipes, both in centigrade degrees,^ = height
of barometer in millimetres, and m a coefficient of radiation.
Reduced to British units and 30 inches of the barometer, the formula becomes
u = total units emitted per square foot per hour by radiation and convection
— mx 1.00427^ (i.oo427<— i) + 0.2853 X / 1.233.
P^clet found the value of »i = 124.76 for iron.
Mr. Anderson's experiments on hot water pipes gave m ^ 122 for cast-iron pipes,
and m » 250 for wrought-iron pipes. Proc. Inst. C. £. vol. xlviii.
104 Observations on Warming.
An open fire warms the air in a room by first warming the
walls, floor, ceiling, and articles in the room, and these in
their turn warm the air. Therefore in a room with an open
fire, the air of the room is, as a rule, less heated than the
walls. In this case the warming of the air depends on the
capacity of the surfaces to absorb or emit heat ; except that
the heat received by the walls may be divided into two parts,
one part heating the air in contact with the wall, and the
other passing through the wall to the outer surface, where it is
finally dissipated and wasted.
In a close stove heated to a moderate temperature, the
heat, as it passes from the fire, warms the surface of the
materials which enclose and are in contact with the fire and
with the heated gases, and transfers the heat through the
materials to the outer surface in contact with the air ; and the
air is warmed by the agency of this outer surface. If heated
to high temperatures it gives out radiant heat, which passes
through the air and warms the objects on which the rays
impinge.
With hot-water pipes, the heat from the water heats the
inner surface of the pipe, and this surface transfers its heat to
the outer surface through the material of the pipes. The rate
at which the heat can pass from the. inner to the outer surface,
and be thus utilised instead of passing away straight into the
chimney, depends on the heat evolved by the fire, on the
extent of surfaces exposed to the heat, on th^ir capacity to
absorb and emit heat, and on the quality of the material
between the inner and outer surface as a good or bad con-
ductor of heat.
The passage of heat through a body by conduction varies
directly with the quality of material and with the difference
between the temperature of the inner surface exposed to the
heat and the outer surface exposed to a cooling influence, and
inversely as the thickness between the surfaces.
Observations on Warming. 105
\l E =. loss by conduction,
C = conducting power of the material,
f = temperature of heated surface,
/ = temperature of cooler surface,
G = thickness of material,
then E = ^-S^.
The following is the quantity of heat in units transmitted
per square foot per hour by a plate one inch in thickness,
with a difference of 1° Fahrenheit between the temperature
of the two sides of the plate : —
Copper 515
Iron 233
Lead 113
Stone (calcareous) 13*68
Glass 6-6
Brickwork 4-83
Plaster 3-86
Wood, fir parallel to the fibres ... T'37
„ fir perpendicular to the fibre's . . '75
Wool -33
Thus, Other things being equal, copper is a better material
than iron for conveying the heat from the fire to water or air ;
and coverings of brickwork, wood, or woollen fabrics are
better adapted than iron for retaining the heat. The pro-
perty which appears more than any other to make materials
good non-conductors of heat is their porosity to air, and the
fact that they retain air in their pores ; air being a very bad
conductor of heat.
The direct warming of the air may be effected by stoves
with brick or iron flues, or by hot-water or steam pipes. The
sizes of the heating surfaces for this object must be propor-
tioned to the volume of air required and to the degree of heat
to be maintained ; and it should also bear a proportion to
the thickness and the capacity of the material for absorbing
and radiating heat and for transferring heat from" one surface
to the other. When a large volume of air is supplied and
io6 Observations on Warming.
removed for ventilation, rapidity in transferring the heat from
the fuel to the air is an important consideration.
Brick stoves and flues are worse conductors of heat than iron
stoves or flues ; therefore the heat generated in a brick stove
passes more slowly to the outer surface ; but the surface of a
brick stove parts with the heat which reaches it somewhat more
rapidly than do the surfaces of an iron stove. The slow con-
ducting power of the material, and the greater thickness, of a
brick stove, prevent alternations which may take place in the
fire from being felt so much as with iron stoves or flues ; and
therefore the brick stove warms the air more equably, without
sudden variations ; the air so warmed is free from objectionable
effects; and where they can be conveniently applied, it is advis-
able to use brick stoves for warming air for ventilating purposes.
With an iron flue-pipe from a stove, almost the whole heat
which any fuel is capable of developing may be utilised by
using a long flue-pipe, horizontal for the greater part of its
length, to convey the products of combustion to the outer air.
The heat given out by- a stove-pipe varies with the tempera-
ture from end to end, being of course greatest at the end next
the stove, where the loss of heat is very rapid ; and the
amount of heat given out per square foot will vary at each
point as the distance from the stove increases ; and thus- in
dividing the pipe into lengths, each giving out an equal
amount of heat, the length of the portion of pipe at the end
further from the stove would be considerable, whilst the length
required to give out an equal amount of heat near the stove
would be very short. But not only does the amount of heat
given out vary greatly from end to end of the flue-pipe, but
the proportions into which the heat divides itself between the
walls and the air vary greatly with the temperature.
Thus, with a stove-pipe heated at the end nearest the stove
to a dull red heat of 1 230*^ Fahr., and of sufficient length to
allow the heat to be diminished to 150° at the further end, it
would be found that at the stove end of the flue-pipe 92 per
Observations on Warming. 107
cent, of the total heat emitted by the pipe is given out by
radiation to the walls, and only 8 per cent, to the air ; but at
the exit end the heat is nearly equally divided, the walls
receiving ^^ and the air 45 per cent. Taking the whole
length of such a pipe, the walls would receive 74 per cent, and
the air %6 per cent, of the heat emitted. But with a flue-pipe
heated to lower temperatures the air might receive half the
heat or even more.
When therefore the object is to heat the walls rather than
the air, which is sometimes the case, the temperature of the
pipes should be high, and for this purpose stove pipes are
more effective than hot-water pipes, or low-pressure steam
pipes. Hot-water pipes heated under pressure on Perkins'
system, and high-pressure steam pipes would radiate a pro-
portion of heat to warm the walls.
At high temperatures there will be practically little dif-
ference of effect between horizontal and vertical flue-pipes,
because the heat given out is principally that due to radiation,
which is independent of the form and position of the radiant.
An adequate proportion of flue-pipes to the form and size
of the stove involves a large surface for the flue-pipe ; and
with a careful observance of proportion, as much as 94^ per
cent, of the heat in the fuel has been utilised, only 5J per
cent, being carried away.
In deciding on the proper height of the flue-pipe as a
chimney for a stove, it is necessary to consider the three
cases of (i) a vertical flue-pipe and of a pipe with a uniform
upward slope, {%) of a pipe with the part next the stove ver-
tical while the rest is horizontal, and (3) of a pipe with the
part next the stove horizontal and the vertical part at the
exit end.
The mean temperature of the internal air in the flue
regulates the discharge which, after allowing for friction, is
due to the difference in vertical height between the stove end
of the flue and the chimney end. Therefore, in the first case
io8 Observations on Warming.
— viz. with a flue either vertical or with a uniform slope — the
mean temperature of the flue may be taken. In the second
case, the high temperature at the vertical part of the flue may
render a shorter vertical flue equally efficient with the inclined
flue ; but in the case where the horizontal part of the flue is
nearest to the fire, and the vertical part the furthest removed
from it, the temperature in the vertical part of the flue will be
lower, being further from the stove, and the height of the vertical
portion must be greater than that of the uniformly inclined flue.
There are however several serious objections to iron stoves,
especially for small rooms. A long flue-pipe is unsightly, and
on that account often inadmissible.
Iron stoves heat rapidly, and easily become red-hot, there-
fore the effect produced is unequal both on the air and on
persons in the vicinity of the stove. An iron stove cools down
with rapidity when the fire is low. The flue-pipe gives out
unequal degrees of heat in the different parts of its length.
With an iron stove the temperature at i8 inches from the stove
has been found to exceed by 37° Fahrenheit that observed at
6 feet from it ; and with a red-hot stove the difference in that
short distance was in some cases as much as 45^
Carbonic oxide has been found in air heated by iron stoves.
This can only occur provided the stove be very highly heated ;
but a high temperature is a liability to which iron stoves are
subject. Iron very highly heated may take up the oxygen
from the carbonic acid prevalent in the air of an occupied
room, and thus reduce the carbonic acid to the condition of
carbonic oxide. Moreover, the quantity of dust in a room,
which almost always contains organic matter, may under
these conditions of temperature somewhat influence the
presence of carbonic oxide.
General Morin alleges that he found these eflfects to be
nearly three times as great with cast-iron as with wrought-
iron stoves. It has also been alleged that the carbonic oxide
generated in the fire may permeate through the cast iron of
Observations on Warming. 109
the stove, if very highly heated or of inferior porous metal, into
the surrounding air. Carbonic oxide may also be produced
by the oxygen of the air acting on the carbon in the cast iron
if heated to a red heat. The effect would be diminished by
the presence of moisture in the air. Consequently the use of
vessels containing water on metal stoves has been recom-
mended. Whatever may be the value of these allegations,
the use of surfaces of iron heated to a red heat for warming
air for ventilating purposes is seriously objectionable. Hence,
whenever iron stoves or cockles are used for heating air, care
should be taken to prevent the iron from attaining a high
temperature, and with this object all iron stoves should have
a lining of fire-brick, so as to prevent the fire from coming in
direct contact with the iron ; such an arrangement prevents
these inconveniences, and preserves greater regularity in the
heating of the air. An advantageous arrangement would be
to provide the iron with an outer surface of glazed enamel,
because the iron would convey the heat rapidly from the fire
to the surface, while the enamel surface would emit the heat
more rapidly than the iron surface.
Hot-water pipes for warming air are free from many of the
objections arising from the direct application of heat to iron,
because the heat can be regulated with exactness.
Water boils at ii%^ Fahrenheit under the atmospheric
pressure of I4'7 lbs. per square inch, or 30 inches of mercury,
i.e. at about the sea level. Under one-half that pressure,
viz. 7«3 lbs. per square inch, or 15 inches of mercury, it boils
at 180° ; and under a pressure of four atmospheres above the
ordinary atmospheric pressure, or 44 lbs. per square inch, it
boils at 291°; and under a pressure of 10 atmospheres, or
132 lbs. per square inch, it boils at 357° Fahrenheit. Thus
a high temperature may be obtained from water without
generating steam by heating it under pressure. Salt water,
saturated with \i*% lbs. of salt per 100 lbs. of water, boils at
227"*, and freezes at about the zero of Fahrenheit.
no Observations on Warming.
Steam is generated under the mean atmospheric pressure
of 30 inches of mercury when the boiling-point is attained,
i. e. Tti'f ; but before the water becomes vapour, such further
amount of heat equal to 966° is absorbed and becomes latent
as would sujffice to raise the water to 1178° if it did not turn
into steam. The temperature of 11 78**, which is thus required
to produce steam, is necessarily constant, and consequently a
greater or less amount of heat becomes latent according as
the pressure is below or above the atmospheric pressure.
This latent heat is given out on the reconversion of steam
into water.
Pipes may be heated either by hot water or by steam.
The higher the temperature, the greater is their comparative
effect on the warming of air. Thus pipes heated by hot water
under pressure convey heat to the air with greater rapidity
than pipes heated by hot water at low pressures ; and steam
pipes are more effective than hot-water pipes ; and steam at a
high pressure is more effective than low-pressure steam. One
advantage of heating by steam or by water under considerable
pressure is the high temperature obtained in the pipes, and
the consequent radiation of a larger proportion of heat to the
walls of a room, than takes place with pipes heated under
ordinary pressures. When steam is employed to warm air
for ventilating purposes it is often necessary to adopt special
means to moderate the temperature in warm weather.
There is moreover some practical inconvenience attending
the use of high-pressure steam in localities where an ex-
perienced workman is not near at hand. For this reason,
hot-water pipes have been generally preferred for warming
ordinary houses.
The efficient action of hot-water pipes depends upon the
upward flow of the heated and expanded water, as it passes
from the boiler, being made as direct as possible, and so pro-
tected as to lose little heat between the boiler and the place
where the heat- is to be utilised. The return pipe, which
Observations on Warming. iit
brings back the water to the boiler after it has been cooled
down by the abstraction of heat in warming the air, should be
passed in to the bottom of the boiler as directly, and in as
uniform a line from the place where the heat has been used, as
possible. The velocity of flow in the pipes will depend upon
the temperature at which the water leaves the boiler, the height
to which the heated water has to rise, and the temperature at
which it passes down the return pipe back into the boiler.
The efficiency of a hot-water apparatus will be regulated by
these conditions, by the sizes of the pipes, and by such other
conditions as affect the flow of water in pipes.
It will be evident that to obtain an equal velocity of flow
when the height of the vertical column is small, the tempera-
ture at which the water returns to the boiler must be lower
than when the vertical column is long. Therefore when the
boiler or source of heat is very near the level of the pipes
for heating the air, the average temperature which can be
obtained in the pipes will be lower than when the vertical
column is long. Hence, the heating surface of the boiler,
the area of the grate which regulates the flow of air to the
fuel, and the surface of pipe which enables the heat from the
boiler to be utilised, must be regulated with reference to this
difference of level.
It may further be assumed that with small pipes, the
temperature being constant, the velocity of flow in the pipe
necessary to furnish a given amount of heat will vary in the
ratio of the length of the pipe.
When the water circulates through the pipes by virtue of
the difference of temperature of the flow and return currents
only, it is impossible to count upon a greater mean tempera-
ture in the pipes than from i6o° to i8o°, because above that
temperature the water in the boiler begins to boil, and causes
an overflow of the supply cistern and escape of steam at the
air pipes. In order to obtain a sufficient velocity of circu-
lation for long distances, or with small differences of level, a
112 Observations on Warming.
V
forced circulation may be resorted to, as has been done by-
Messrs. Easton and Anderson at the County Lunatic Asylum
at Banstead.
There two pipes are laid side by side, one of which com-
municates with the boilers and is termed the flow-pipe; the
other, termed the return-pipe, is connected with the feed-
cistern for the boilers, which cistern is situated above the
level of the boilers.
Both pipes are connected with the various coils to which
the heated water is desired to be conveyed, by valves which
can be opened or closed at wilL An Archimedean screw
pump is fixed on the return-pipe near the point where the
pipe ascends into the cistern. This pump is always kept at
work. When the communications between the flow and
return pipes are closed, the screw simply slips through the
water; as soon as any communication is opened, the screw
draws the water along the pipe, and forces it into the cistern,
thus ensuring a constant circulation.
By Perkins' system the water is heated under considerable
pressure, and a higher temperature is thus obtainable than
with ordinary pressures.
In its simplest form the apparatus consists of a continuous
or endless iron tube of about one inch diameter, closed in all
parts and filled with water. The joints are screw-joints
connected within a socket forming a right and left hand
screw. About one-sixth part of the tube is coiled in any
suitable form and placed in the furnace, forming the heating
surface, and the other five-sixths are heated by the circu-
lation of the water which flows from the top of this coil ; and
after having been cooled in its progress through the building,
returns to the bottom of the coil to be re-heated.
Water when heated from 39^1 to 212^ Fahrenheit expands
about 5 per cent, of its original bulk. Therefore, in order
to provide for the increased volume of the water when
heated, a tube called an expansion tube is placed above the
Observations on Warming-, 113
highest level of the smaller tubes which convey the heat to
the distant parts of the building.
This tube is of larger diameter than those used as heating
surfaces, and its length and capacity are proportioned to the
quantity of tube to which it is attached.
The filling tube of the apparatus is placed on a level with
the bottom of this expansion tube so as perfectly to fill all
the small tubes, and yet prevent the possibility of filling the
expansion tube itself. The expansion tube being then left
empty, allows the water as it becomes heated to expand with-
out endangering the bursting of the smaller tubes.
The apparatus is filled by an opening connected with the
lowest line of tubing, so that the water, as it rises, drives the
air before it, and out through an opening in the expansion
tube. Great care must be taken to expel all air from the
pipes by repeatedly forcing water through them. When the
pipes are filled, both the opening in the filling tubes and the
opening in the expansion tube are closed by screw-plugs.
The form and size of the furnace varies according to the
locality and the work the pipes have to do.
A temperature of as much as 300° Fahrenheit can be
obtained in the tubes.
Steam in lieu of hot water is especially applicable, either
where steam for other purposes is in use, as for instance where
the exhaust steam from an engine is available, or where heating
is required on a large scale.
Where exhaust steam is used it may be assumed that the
capacity of heating is almost in a ratio with the fuel ex-
pended under the boiler. There is some cooling in passing
through the engine, and along the pipes to the rooms requir-
ing to be heated, but this is slight if the pipes and cylinder
are covered with a good non-conducting material, so that the
condensed water may be taken back hot into the boiler.
So far as economy in heating is concerned, there is not
much difference between the use of exhaust steam and of that
I
H4 , Observations on Warming'^
taken direct from the boiler. For instance, if the steam is
taken from the boiler direct to the pipes at five atmospheres,
the temperature would be a little over 300°. If, on th^ other
hand, a comparative capacity of steam were allowed to pass
' through the engine to create power, and discharged into the
pipes at one atmosphere, it would decrease in temperature to
something over 7,12^ ^ but it would increase in bulk according
to the expansion ; and by an increased heating surface a larger
proportion of beat can be practically utilised than shown by
the difference of the temperature.
As regards t^e extent to which exhaust steam can be
carried, Mr. Boultqn, who has perfected this system, mentions
a case in which fropi an engine of ^5 horse power nominal,
with a 17-inch cylinder, the exhaust steam travels about iioo
yards in a direct line, and passes along various branches,^
amounting in the aggregate to about ^^386 yards, or i J miles
of li-inch pipes, and then into the tank to warm the feed
water for the boiler.
The use of steam for heating on a large scale is exemplified
in many of our principal buildings, and amongst others in the
Houses of Parliament. An interesting application of steam
for heating, is that adopted at Lockport, a town in the United
States, of which a description has been given by Mr. George
Maw; the object i^ this c^se being to avoid the necessity of
having separate fires itx each house.
Two hundred houses were heated from the central supply
through about three miles of pipiag, radiating from the boiler-
house ; this building contained two boilers each 16 ft. by 5 ft.,
and one boiler of about half the size. The steam during the
winter was maintained at a pressure of 35 lbs. to the inch, with
a consumption of four tons of anthracite coal in 24 hours.
This boiler pressure of 35 lbs. was maintained through the
entire length of the three miles of main piping up to the
points of consumption, at each of which there is a cut-off
under the control of the consumers.
Observations on Warming. 115
The first 600 feet of mains from the boilers are 4 inches
in diameter. There are 1400 feet of 3-inch pipes ; 1500 ft. of
2j-inch pipes ; and 2000 feet of a-inch pipes. The supply-
pipes from these mains to the houses are li-inch in diameter,
and within each house f-inch pipes are used. In addition to
the cut-off tap from the main under the control of the con-
sumer there is a pressure-valve regulated to a 5 lb. pressure
under the control of the company, and beyond this is an
ingeniously constructed meter, which not only indicates the
total consumption in cubic feet of steam, but also the quantity
of steam used in each apartment. At each 100 feet of main
an expansion-valve like an ordinary piston and socket is
inserted, allowing an expansion in each section of 100 ft. of
i|-inch for the heat at 35 lbs. pressure. No condensation
occurs in the mains. They are covered with a thin layer of
asbestos paper next the iron, then a wrapping of Russian felt,
and are finally wrapped round with Manilla paper like smooth
light brown paper, and the whole encased in timber bored out
three-quarters of an inch larger than the covered pipes, and
laid along the streets like gas pipes.
The distribution of heat in the apartments is by means of
radiators, consisting of inch pipes 30 inches long placed ver-
tically either in a circle or in a double row, and connected
together top and bottom ; they are furnished with an outlet
pipe for the condensed water which escapes at a temperature
a little below boiling, sufficient in quantity for the domestic
purposes of the house, or it may be used as accessory heating
power for horticultural and other purposes.
The steam was also applied at a distance of over half a mile
from the boilers for motive power, and it was stated that two
steam engines of lo-horse and 14-horse power were occasionally
worked from the boilers at a distance of half a mile with but
a slightly increased consumption of fuel.
The laid-on steam was used for cooking purposes, for boiling,
and even baking ; in a house three-quarters of a mile from the
I %
ii6
Observations on Warming.
boilers, a bucket of cold water could be raised to boiling heat
in three minutes, by the passage of the steam through a
perforated nozzle plunged into the bucket.
As in the case of gas supply, the Steam Supply Company
lay their pipes up to the houses, the consumer paying for all
internal pipes, fittings, and radiators.
. In a moderately-sized eight-roomed house the expenses of
these amounted to 150 dollars, or a trifle over £'>p^ and in
larger houses with more expensive fittings to 500 dollars, or
about ;^ioo.
The working expenses consist of but little more than the
coal and the wages of two firemen.
700
650
600
550
50O
450
400
550
300
260
eoo
150
100
so
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y
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t
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i
ij!
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4
^
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it*""
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5U.
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,-'
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z^
,-»'
^^
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-"'
700
660
600
560
500
4-50
4-00
350
300
250
eoo
150
100
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^^^^^ ___^^
Difference of \^ 20° 30" 40" so** eo** 70** ao" so** 100° no" 120° 130° 140° 150*^160 Mo'\9^\9Q2Qfi^TtTivpcralun.
Fig. 18.
The annexed diagram (Fig. i8), resulting from Mr. Ander-
son's experiments, is published in the Journal of the Institution
of Civil Engineers for 1877, and shows the total units of heat
given out by cast-iron and wrought-iron pipes per square foot
of surface per hour for various differences of temperature,
applicable either to hot-water or steam pipes.
Suppose, for example, it is required to know how much
Observations on Warming. 117
heat will be given out by 4-inch pipes at 190® in a room, the
temperature of which is 60°, the difference of temperature
being 130°: look along the line of abscissae for 130, and the
ordinate then gives 2327 units for 4-inch pipes, and '>^^6 units
for a-inch wrought-iron pipes per square foot per hour.
When the form of apparatus for heating has been decided
on, the amount of heating surface to be afforded for purposes
of ventilation and warming depends mainly upon the volume
of air to be admitted and removed, and the temperature
desired to be maintained ; but in any given building there
are other circumstances to be taken into account — viz. the
position, aspect, subsoil, temperature of locality, shape and
size of building, extent, position, and thickness of walls, size
and form of windows, skylights, and suchlike matters, which
affect either the temperature of the incoming air or the con-
ditions which determine the loss of heat in a building.
A rough empirical rule is suggested by Mr. Anderson for
hot-water pipes in this country — viz. that i square foot of
heating surface is required for every 6^ cubic feet of content
of the space to be warmed, and in a greenhouse i square foot
to every 24 cubic feet. This empirical rule does not however
appear to be based on the important sanitary considerations
of the renewal of air. A similar rough approximate rule for
pipes heated with exhaust steam has been given by Mr.
Boulton as follows : i superficial foot of steam pipe for each
6 superficial feet of glass in the windows ; i superficial foot
of steam pipe for every 6 cubic feet of air removed for
ventilating purposes per minute, i superficial foot of steam
pipe for every 120 superficial feet of wall, roof, or ceiling,
allowing about 15 per cent, on the amount thus obtained for
contingencies. He states that, roughly speaking, the exhaust
steam due to one-horse power can be made to warm 30,000
cubic feet of space.
If the fresh air for ventilation is warmed in underground
chambers, such places should be so formed as to be dry and
ii8 Observations on Warming.
well-drained, and the channels leading therefrom constructed
of such form and materials that the air shall lose as little
heat as possible in transmission.
When air is warmed, its capacity for moisture is increased;
thus if air at 3a** Fahrenheit be in a condition of complete
saturation from moisture, which is represented by 100 degrees,
and if the air be then raised to a temperature of 5^^°, it would
have only 46 degrees of saPturation, and appear to be dry;
whereas if the temperature be raised to 72° Fahrenheit, the
degree of saturation would be diminished to 23 degrees,, and
the air would appear to be extremely dry.
In a damp climate, up to a certain point, the drying of the
air caused by raising the temperature is as much a source of
comfort as the warmth. But when the outer air is dry, the
additional dryness caused by warming the air may in some
cases become inconvenient.
For reasons already mentioned, the open fire does not
directly warm the air to so great an extent as stoves or
heated pipes, therefore the dryness is generally not found to
be objectionable with an open fire. But with stoves or hot-
water pipes, it is frequently necessary to provide vessels of
water on or near the stoves or heated pipes, to supply ad-
ditional vapour to the air when required.
The conclusions which follow from these considerations are,
that where a room is heated by warmed air passed through
flues into the room, without any source of heat in the room itself,
the air imparts its heat to the walls. The air is thus warmer
than the walls. When a room is warmed by an open fire, on
the other hand, the warming is effected by the radiant heat
from the fire ; the rays from the fire pass through the air
without sensibly warming it, the radiant heat warms the
walls and furniture, and these impart their heat to the air.
Therefore the walls in this case are warmer than the air.
Consequently in two rooms, one warmed by an open fire and
one by hot air, and with air at the same temperature in both
Observations on Warming. 119
rooms, the walls in the room heated by hot air would be some
degrees colder than the air, and therefore colder than the
walls of the room heated by ail open fire, and these colder
walls would therefore abstract heat from the occupants by
radiation more rapidly than would be the case in the room
heated by an open fire. And to bring the walls up to the
same temperature in the former case — ^viz. in the room heated
with hot air — the air of the room would require to be heated
to an amount beyond that necessary for comfort, and therefore
to a greater amount than is desintble oii sanitary grounds,
seeing that warmed air contains less oxygeii than cooler air.
As sick persons are more sensitive to such influences than
persons in health, this would appear to be the reason why
in hospital wards the Warming by means of an open fire has
been always recognised as preferable to warming by hot air.
To a certain extent, dependent on the temperature of the
heating surface, a similar effect takes place in rooms warmed
by close stoves, hot-water pipes, or low-pressufe steam pipes ;
but in a room warmed by steani pipes heated to a high tem-
perature, the effect on the walls would tend to approximate
in some degree to that produced by the open fire in pro-
portion as the temperature of the pipes is raised. Where
the object is to warm the walls as well as the air, high-pressure
steam is a more advantageous mode of heating than hot-water
pipes.
CHAPTER XI.
ACTION OF OPEN FIREPLACES ON VENTILATION.
One pound of coal is far more than sufficient, if all the
heat of combustion is utilised, to raise the temperature of a
room, 2,0 feet square and 12, feet high, to 10 degrees above the
temperature of the outer air. If the room were not ventilated
at all, and the walls were composed of non-conducting mate-
rials, the consumption of fuel to maintain this temperature
would be very small ; but, in proportion to the change of the
air of the room and to the escape of heat through the walls,
windows, ceiling, &c., so would the consumption of fuel neces-
sary to maintain that temperature increase. If the volume
of air contained in the room above mentioned were changed
every hour, one pound of coal additional would be required
per hour to heat the inflowing air, so that to maintain the
temperature at 10 degrees above that of the outer air during
I z hours would require 1 2 lbs. of coal.
The principle of the ordinary open fireplace is that the
coal shall be placed in a grate, to which air is admitted from
the bottom and sides to aid in the combustion of the coal ;
and an ordinary fireplace, for a room of 2,0 feet square and 1 2
feet high, will contain from about 15 to 30 lbs. at a time, and,
if the fire be kept up for 12 hours, probably the consumption
will be about 100 lbs., or the consumption may be assumed at
about 8 lbs. of coal an hour.
As already mentioned, the radiant heat from the fire does
not warm the air of the room ; the rays from the fire war^m
the sides and back and parts adjacent to the grate, they warm
Action of Open Fireplaces on Ventilation. 121
the walls, floors, ceiling, and furniture of the room, and these
impart heat to the air. The form and material of the fire-
place can thus assist materially the warming of the air. The
rays should impinge more freely on the walls and floor than
on the ceiling. A projecting chimney-piece with a surface
favourable to the absorption and emission of heat would be
more favourable to the warming and circulation of the air
than one which would allow the rays to pass to the ceiling.
In an ordinary fireplace the sides should be splayed, as in
the Rumford form of grate ; the sides and back should be of
non-conducting material, with a surface favourable to the rapid
absorption and emission of heat. Thus brick or tiles are better
than iron for this purpose. Similarly, the degree to which the
materials of the walls or floor of the room are unfavourable to
conduction but favourable to the absorption and emission of heat
will have a bearing on the capacity of the room for warmth.
One pound of coal may be assumed to require, for its per-
fect combustion, 160 cubic feet of atmospheric air; 8 lbs.
would require i,:z8o cubic feet ; but at a very low computa-
tion of the velocity of the gases in an ordinary chimney-flue
the air would pass up the chimney at a rate of from 4 to 6
feet per second, or from 14,000 to iio,ooo cubic feet per hour ;
with the chimneys in ordinary use, a velocity of from 10 to
15 feet per second often prevails, giving an outflow of air of
from 35,000 to 40,000 cubic feet per hour. This air comes
into the room cold, and when it is beginning to be warmed it
is drawn away up the chimney, and its place filled by fresh
cold air. A room 20 feet square and \% feet high contains
4,800 cubic feet of space. In such a room, with a good fire,
the air would be removed four or five times an hour with
a moderate draught in the chimney, and six or eight times with
a blazing fire. The atmosphere of the room is thus being
cooled down rapidly by the continued influx of cold air to
supply the place of the warmer air drawn up the chimney ;
and General Morin estimated that of the heat generated by
122 Action of Open Fireplaces
fuel in an ordinary open fireplace about one eighth only is
utilised in the room. The very means adopted to heat the
room tends to produce draughts, because the stronger the
direct radiation, or rather the brighter the flame in open
fireplaces, the stronger must be the draught of the fire and
the abstraction of heat-
A fireplace is thus powerful enough to draw into the room all
the air it wants ; and for this purpose will use indiscriminately
all other openings, whether inlets or outlets if necessary.
The only way to prevent draughts is to adopt means for pro-
viding fresh warmed air to supply the place of that removed.
Fig. 19. Sketch of Experiment made by Mr. Campbell in 1S57 showing the
movement of currents of air in a room with an open fireplace.
The way in which an ordinary open fireplace acts to create
circulation of air in a room with closed doors and windows, is
as follows : — The air is drawn along the floor towards the
grate ; it is then warmed by the heat which pervades all
objects near the fire, and part is carried up the chimney with
the smoke, whilst the remainder, partly in consequence of the
warmth it has acquired from the fire, and partly owing to the
impetus created in its movement towards the fire, flows up-
wards towards the ceiling near the chimney-breast It passes
along the ceiling, and as it cools in its prepress towards the
on Ventilation. 123
opposite wall, descends to the floor, to be again drawn towards
the fireplace.
It follows from this, that with an open fireplace in a room,
the best position in which to deliver the fresh air required to
take the place of that which has passed up the chimney, is
above the projecting chimney-piece, and at any convenient
point in the chimney breast, between the chimney-piece and
the top of the room, for the air thus falls into the warmer
upward current, and mixes with the air of the room, without
perceptible disturbance ; and it also follows that if two fire-
places be placed in a room, they should, unless the room be
very large, both be on the same side of the room, and if shafts
are required for ventilating a room in addition to the open
fireplace, they also should be placed on the same side of the
room as the fireplace, but as far from it as possible.
The open fireplace thus presents special advantages for
securing efficient ventilation by means of the circulation of air
which it creates. It makes the room in which it is in use
independent of other means of extraction of air, unless the
room is very crowded, or beyond the size for which the fire-
place is calculated.
The air thus extracted must be drawn into the room from
somewhere, and unless arrangements be made for supplying
the room with warmed fresh air, cold air finds its way into
the room through the special inlets, if any are provided ; if not,
through the chinks of the windows and doors, or wherever it
can get in most easily. The large volume of fresh air required
to supply that drawn up the chimney cannot always be
warmed with sufficient rapidity by contact with the walls and
furniture only ; the temperature in different parts of the room
is therefore frequently very unequal, and the occupants are
subjected to draughts ; and if there are two fireplaces in the
same room unprovided with special means for the admission
of fresh air, one of which is not lighted, the air is often drawn
down the vacant chimney.
124
Actioft' of Open Fireplaces
It IS therefore desirable in cold weather to replace some
part at least of the air drawn up the chimney by air partially
warmed. This can be effected in various ways, either by a
service of hot-water pipes carried into all the rooms, to coils
placed in front of the fresh-air inlets, so as to warm the fresh
air as it enters the room ; or by bringing warmed air into the
room by flues from a central heating apparatus. But the simplest
plan is to utilise some of the waste heat which in the case of
an ordinary open fireplace passes away unused up the chimney.
Fig. 20. Section of a room with a ventilating grate and warm-air flue,
showing action of Are in producing circulation of air.
The ventilating fireplace was designed with the object of
obviating the above-named objections to the common fire-
place, of utilising spare heat, and of providing such adequate
means of ventilating the soldiers' rooms in cold weather, when
the windows are shut, as would not be liable to be deranged.
Fresh air is admitted to a chamber formed at the back of
the grate, where it is moderately warmed by a large heating
surface, and then carried by a flue, adjacent to the chimney-
flue, to the upper part of the room, where it flows into the
currents which already exist in the room. These grates have
never been patented, and therefore manufacturers do not care
to suggest their use.
on Ventilation. 125
The body of the stove is of the best cast iron, and consists
of three pieces, properly connected by screws. The first piece
forms the moulded projecting frame ; the second the body of
the grate; and the third the nozzle or connexion with the
smoke-flue, the bottom flange of which is bolted to the back
of the grate. The stoves are of three sizes. The largest has
an opening for fire of i ft. 9 in. wide, and was intended for
rooms containing from 7,500 to 10,000 cubic feet ; it weighs
about 3 cwt. I qr. 10 lbs. The second, or medium size, has
an opening for fire i ft. 5 in. wide, and was intended for rooms
containing from 3,600 to 7,500 cubic feet; it weighs about
2 cwt. 3 qrs. 5 lbs. The third, or smallest size, has an opening
for fire 1 ft. 3 in. wide, and was intended for rooms contain-
ing 3,600 cubic feet and under ; it weighs about % cwt. 2 qrs.
The figures appended (Figs. 21-24) show an elevation,
section, and plan of the second or medium-size stove, the
extreme dimensions of which are 40 inches wide by 42 inches
high. The projecting moulded frame enables the stove to
be applied to any existing chimney-opening.
The fireplace has a lining of fire-lumps in five pieces — two
sides, one back-piece, and two bottom-pieces, moulded to the
form shown in the woodcut. The object of this fire-clay
lining or cradle is to prevent the contact of the incandescent
fuel with the iron, and to preserve a high uniform temperature
in the vicinity of the fuel to assist the combustion.
The bottom is partly solid, being made of two fire-lumps
placed one on each side, and supporting an intermediate cast-
iron fire-grating, which occupies about one-third of the bottom
of the grate ; by this means, whilst the draught is checked
by the solid part of the bottom of the grate, and the con-
sumption of fuel reduced, a sufficient supply of air is obtained
for combustion through the grating to secure a cheerful fire.
A clear space, half an inch deep, is formed between the back
piece of fire-lump and the iron back of the grate, through
which a supply of air passes from the ash-pit under the grate,
126
Action of Open Fireplaces
and through a slit in the fire-lump, on to the upper part of the
back of the fire. The air thus brought into contact with the
heated coal is received at a high temperature, in consequence
of passing through the heated fire-lump, and is forced into
contact with the gases from the coal by means of the piece of
fire-lump which projects over the fire at the back of the grate ;
and thus a more perfect combustion of the fuel is effected than
with an ordinary grate, and the creation of smoke is pre-
vented : in fact, with care, almost perfect combustion of the
fuel, and consequent utilisation of the heat, can be obtained.
Whilst the incandescent fuel and flame are kept away from
actual contact with the iron back of the stove, the heated
on Ventilation. 127
gases from combustion, and such small amount of smoke as
exists, are compelled, by the form of the back of the grate,
and the iron part of the smoke-flue, to impinge upon a large
heating surface, so that as much heat as possible may be
extracted from the gases before they pass into the chim-
ney ; the heat thus extracted is employed to warm air taken
directly from the outer air. The air is warmed by the iron
back of the stove and smoke-flue, upon both of which several
broad flanges are cast, so as to obtain a large surface of metal
to give off" the heat. This giving-off" surface (amounting in the
case of No. i grate to about 18 square feet) is sufficient to
prevent the fire from ever rendering the back of the grate so
hot as to injure the air which it is employed to heat. The
fresh air, after it has been warmed, is passed into the room
near the ceiling by the flue shown in the woodcut.
The flue which has been adopted for barracks is carried up
by the side of the smoke-flue in the chimney-breast.
In order to afford facilities for the occasional cleansing of
the air-chamber, and those parts of the air-channels connected
with it, the front of the stove is secured by screws, so that
it can be easily removed, thus rendering the air-chambers
accessible.
The stove was designed with tte object of being applied
to existing chimney-openings. In so applying it, the air-
chamber is to be left as large as possible, thoroughly cleansed
from old soot, rendered with cement, and lime-whited. Should
the fireplace be deeper than i foot 6 inches, which is the depth
required for the curved iron smoke-flue, then a lining of brick-
work is to be built up at the back to reduce it to that
dimension. The chimney-bars, if too high, must be lowered
to suit the height of the stove, or to a height above the hearth
of 3 feet 3 inches ; they must also be straightened, to receive
the covering of the air-chambers. These coverings should be
of 3-inch York or other flagging, cut out to receive the curved
iron smoke-flue, and also to form the bottom of the warm-air
128 Action of Open Fireplaces
flue in the chimney-breast ; or the covering may be formed
of a brick arch. In new buildings the air-chambers may be
rectangular; they must be 4 inches narrower than the ex-
treme dimensions of the moulded frame of the stove, so as to
give a margin of 1 inches in width all round for a bedding of
hair mortar. In existing buildings, the recess in which an
ordinary firegrate would be fixed forms the chamber in
which the air is warmed. Great care must be taken in
bedding the several joints to prevent smoke from the flue
passing into the fresh-air chamber or fresh-air flue.
The mode of admitting external air into this chamber must
depend upon the locality. If the fireplace be built in an
external wall, the opening for fresh air can be made in the
back ; but if in an internal wall, it will be necessary to con-
struct a channel from the outside, either between the floor-
ing of the room and the ceiling-joists of the room below (if
there be independent ceiling-joists), or between the floor-
boards and the plaster ceiling of the room below, in the
spaces between the joists; or by a tube or hollow beam carried
either below the ceiling of the room altogether ; or, as is often
more convenient, behind the skirting of the room in which the
firegrate is placed.
In this country these horizontal ducts should contain a sec-
tional area, for the large size grates of 84 square inches, for the
medium size of 60 square inches, for the smaller size of 36 square
inches ; the clear area through the grating covering the opening
to the outer air should be equal in area with that of the flue.
If the flues are of considerable length, and with bends, the
sectional area should be rather more than that mentioned,
to allow for friction ; but if there be a direct communication
with the outer air, the sectional area may be rather less than
that recommended. In exceptionally cold weather it may be
advisable to reduce temporarily the area of inlet.
The amount of air delivered through the fresh-air flue
varies somewhat with the direction of the wind. The inlet
on Ventilation, 129
shaft acts best when the windows, doors, and other inlets to
the room are closed, as it then becomes the sole inlet for fresh
air for the room.
In the ventilation of barrack-rooms or hospitals, it was not
intended that the fresh air warmed by the grate should be
the whole supply of fresh air, nor that the chimney should be
the sole means employed for the removal of the air to be
extracted. In ordinary houses, however, the grate, if adopted,
might be used in such a manner as to perform the whole
functions of ventilation. In this case it is of course necessary
to remember that the ventilating power is a fixed quantity,
and that in originally settling the size of a grate for a par-
ticular room it will be necessary to bear in mind the general
object for which the room is to be employed, and the number
of persons by whom it is required to be occupied with
efficient ventilation, because all experiments show that no
room can be considered even tolerably ventilated as a per-
manent arrangement unless at least icoo cubic feet of air per
occupant are renewed per hour ; consequently a room lo feet
long by 15 feet wide and 10 feet high (i. e. with 3000 cubic
feet of space), with three people in it, would not require the
air to be changed much more than once an hour; whilst, if
occupied by twelve or fourteen people, it would require to be
changed five times in an hour. If the normal use of the
room was for three people it would not be worth while to
provide for the extra number by which it might on occasions
be occupied, as their wants in such a temporary case could
be met by opening the windows slightly at the top.
There is one point connected with the fresh-air flue which
must be carefully attended to — viz. the fresh air should be
taken from places where impurities cannot affect it, and the
flue must be so arranged and constructed as to afford easy
means of being periodically thoroughly examined and cleaned.
In barracks the rule is that such cleansing should take place
at least once a year.
K
1 30 Aclion of Open Fireplaces
The area of the grate of No. i stove is 84 square inches, of
which 58 are solid, and 36
afford space in the centre
forthepassingofair. The .
front is open, and air is
passed on to the coal from
the back in the manner
already described. The
grate will contain about
i8to2olbs.ofcoal; when
the fire is maintained for
fig. ija. from twelve to fifteen
hours, a total consumption of about %-^ lbs. per hour, or
40 lbs. for sixteen hours, will suffice to maintain a good fire.
In new buildings it
would be possible, and
in some cases it might
be desirable, to extend
this heating surface con-
siderably by carrying
up the smoke flueinside
the warm-air flue. But
care must be taken not
to overheat the air. This
plan has been adopted
in the fireplaces for the
wards of the Herbert
Hospital, where the fire-
place is in the centre of
the ward, and the chim-
ney consequently passes
under the floor, and is
f'g- >5*- placed in the centre of
the flue which brings in the fresh air to be warmed by
the fireplace; by this means more than 36 superficial feet
on Ventilation. 131
of heating surface have been obtained for warming the fresh
air in addition to the heating surface afforded by the air flues
in the fireplace. (Figs. ^^ a^ %^ b.)
The fire stands in an iron cradle fitted to the fire-
clay back and sides, and a current of air is brought through
the fire-clay at the back, where it becomes heated, on to
the top of the fire to assist the combustion, and thus pre-
vent smoke. The top of the stove is coved inside, to lead
the smoke easily into the chimney. The main body of the
stove is a mass of fire-clay, with flues cast in it, up which
the fresh air passes from the horizontal air flue already men-
tioned, in which the chimney flue is laid. Thus all parts of
the stove employed to warm the fresh air with which the fire
has direct contact, are of fire-clay. This is especially essen-
tial in hospitals, where every element of possible impurity
of air should be avoided. The sectional area of the fresh-
air flue with this arrangement of grate may be i square inch
for every 100 feet of cubic contents of the spaces to be
warmed, for favourable situation ; but in cold or exposed
localities a less area may be allowed.
The horizontal chimney flue in the Herbert Hospital fire-
places is formed of two layers of sheet iron, separated by a
thin layer of fire-clay, so as to prevent overheating of the
surface, and it is about no square inches in area. The hori-
zontal chimney flue terminates in a vertical flue in the side
wall, which should be rather larger in area than the horizontal
flue. This vertical flue is carried in the upper floors to a
height of double the length of the horizontal flue, and is
carried down to the basement, whence it can be swept. The
points of connection between the horizontal chimney with the
descending flue from the fireplace, and with the ascending flue
in the wall, are very carefully rounded, as this is essential to
assist the passage of the smoke. The horizontal flue is swept
from an opening, to which access is obtained by taking up
a moveable board in the floor, and by pushing a brush along
132
Action of Open Fireplaces
the flue, and thus forcing the soot into the vertical flue,
whence it falls down and is removed at the opening in the
basement.
There is placed a spare flue by the side of the vertical flue,
terminating in a fireplace in the basement, which enables the
vertical flue to be warmed, so as either to make it draw when
the fire is first lighted, or to enable a current to be main-
tained for ventilating purposes through the fireplace when the
fire is not lighted. The portion of floor over the horizontal
flue should be so constructed as to be taken up in order to
enable the air flue to be easily and thoroughly cleaned
periodically.
A. Fire-lump with warm air flue through
back,
B. Warm-air pipe to fit into socket on hob,
in lengths of x ft. 3 in. each.
C. Bend to fit socket of the above pipe.
D. Mouthpiece with louvre front to fit on
bend. One of these, 6 in. long, is
supplied with each range.
Increased heating surface for warming
the fresh air is provided by means of
a grating inside the socket at £.
B
6
Fig. 26.
The principle of these arrangements for utilising to some
extent the heat in the chimney has been adopted for barracks
in the case of grates for married soldiers ; these would be
useful as cottage grates. They have a small oven, and an
on Ventilation, 133
open fire ; warmed air is introduced into the room by means
of an iron flue carried up from the fire-brick lining of the stove
inside the chimney, and introduced into the room near the
ceiling through a louvred opening ; by this means the heat of
the smoke is utilised to warm fresh air admitted to the room,
and prevent draughts.
This description of grate was devised for the purpose of
combining a sufficient power of cooking for a cottage with
great compulsory economy of fuel (see Fig. a6).
It must however be observed, that in proportion as the
heat is removed from the chimney, so is the draught, i.e. the
effect of the chimney as a pumping-engine to remove the air,
diminished, and the combustion of the fuel to some extent
checked.
The limit to which the heat from the fire can be utilised
will be the point at which a sufficient amount of heat is left in
the chimney, to cause an adequate draught, so as to ensure
the combustion of the fuel.
With these ventilating fireplaces in temperate weather,
when windows or other inlets are opened direct from the
fresh air, the entrance of warmed air will be checked, whilst
the ventilation of the room would be continued ; and if
desired, the inlets for warmed air may be provided with
valves to be closed when the fireplace is wanted rather for
ventilation than for warming.
Numerous experiments have been made on the ventilating
fireplace for barracks. These experiments show that the air is
generally admitted into the rooms at a temperature of about
ao°, or from that to 30° Fahr. above that of the outer air. The
design of the grate wa,s intended to preclude the possibility of
such a temperature as would in any way injure the air intro-
duced ; and the experiments made by the late Dr. Parkes in a
hospital ward at Chatham, in April 1864, illustrate the hygro-
metric effect with the grate in use. The difference between
the dry and wet bulbs in the ward varied from 8° to 5°j viz.
134 Action of Open Fireplaces
on the 17th of April, 8-5°; on the i8th, 6° ; on the 19th, ^-^ \
on the aoth, 6*5° ; on the 21st, 5«o°. On examining the record
of the dry and wet bulbs, no evidence was seen at any time
of any unusual or improper dryness of the atmosphere. The
difference between the two bulbs was certainly always greater
in the ward than in the outer air, but the difference was not
material. The temperature of the rooms was invariably found
to be so equable, that when the grate was in full action, and
the windows and other means of ventilation closed, thermo-
meters placed in different parts of the room, near the ceiling
and floor, in corners furthest from the fire, and on the side
nearest to it, but sheltered from the radiating effect of the
fire, did not vary more than about i°Fahr. The variation of
temperature in different parts of a room warmed by a fire, by
radiation, without the action of warmed air, will be found to
be from 4° to 6° Fahr., and sometimes even much more in
cold weather.
General Morin, with the object of utilising the grate as the
sole means of ventilation for a room, lays down the principle
that the whole of the air shall be renewed five times in the
hour. To perform this effectually, it is necessary that the
area of the chimney outlet shall afford about one square inch
of area for every lOO cubic feet of content of the room, and
that the area of the fresh air inlet at its opening into the
room should be enlarged to afford about 14 square inches for
every 100 cubic feet of content of the room ; so as to prevent
the air entering with a rapid current. But on an average this
quantity of air is more than is necessary. The Barrack and
Hospital Improvement Committee's proposal would resolve
itself into this — viz. that the air in barrack-rooms should be
completely changed about twice in an hour (inasmuch as they
required a cubic space of 600 cubic feet per man), and for all
ordinary purposes this would probably suffice; as, however,
this proposal was based on a limited number of occupants,
vith a more crowded room the amount must be increased.
on Ventilation, 135
General Morin's experiments in 1864-5-6, with fireplaces
constructed in the ordinary manner, and with others on the
plan above described, in which the chimney was utilised for
warming the air, showed that whilst with an ordinary fireplace
the heat which is utilised in a room a,mounts only to one eighth
of the heat given off by the coal, or '125, in these fireplaces
the heat utilised in the room was '355 of the heat given off
by the coal, or one third ; therefore, to produce the same
degree of warmth in a room, this grate requires little more
than one third of the quantity of coal required by an ordin-
ary grate. The ventilation of the rooms was at the same
time effected by passing a volume of air through the room
in one hour equal to five times the cubic contents of the
room. An equable temperature was maintained during the
experiment. There was no perceptible draught, and although
the doors fitted badly, scarcely any air was drawn in through
the crevices.
In conclusion, the merits which are claimed for this venti-
lating fireplace are : —
1. That it ventilates the room.
2. That it maintains an equable temperature in all parts of
the room, and prevents draughts.
3. That the heat from radiation is thrown into the room *
better than from other grates.
4. That the fire-brick lining prevents the fire from going
out, even when left untouched for a long time, and prevents
the rapid changes of temperature which occur in rooms in cold
weather from that cause.
5. That it economises fuel partly by making use of the
spare heat, which otherwise would all pass up the chimney, and
partly by ensuring by its construction a more complete com-
bustion, and thereby diminishing smoke.
6. That it prevents smoky chimneys, by the ample supply of
warmed air to the room, and by the draught created in the
neck of the chimney.
CHAPTER XII.
VENTILATION IN COMBINATION WITH WARMED AIR IN
ROOMS WHERE OPEN FIREPLACES ARE NOT IN USE.
The open fireplace is convenient in ordinary living-rooms
in this climate, because, the weather is generally so temperate
that it is only exceptionally necessary to provide much
artificial warmth. In climates with colder winters the open
fireplace becomes expensive, and is used rather as a luxury,
because every room and corridor requires to be warmed, and
if this is done by open fireplaces the carrying of the fuel alone
in such cases becomes a serious inconvenience.
In order to ensure an adequate change of air in cold
climates when there is no open fireplace, and when the
weather requires closed windows, and in hot climates when
the movement of air is very small, the fresh air ought to be
^ introduced or extracted by air-flues connected with fans,
pumps, or heated extraction-shafts.
This, however, has not hitherto always been the practice.
In many cases, rooms are warmed by close stoves on the
French or German plan, or by hot water pipes, without any
arrangements for introducing fresh air. On the other hand,
when the warming is effected by an inflow of warm air, the
air is generally brought in by special channels from a heating
apparatus placed in a central part of the building. This latter
plan is much used in the United States, and in Canada, where
the winters are very cold. The warmed air is supplied (gener-
ally at a high temperature) from a heating apparatus which is
usually placed in the basement or lower part of the house.
Ventilation combined with Wai^med Air. 137
The effect of introducing warm air at the lower part of a ward
on each side, and allowing it to escape at the top, was illustrated
by a series of careful experiments, by Professor E. Wood of
Harvard University, upon the various currents prevailing at
the same time in a hospital ward at Boston, U. S. (Fig. 27.)
The ward was 96 feet long by 26 feet 3 inches wide, with
seven opposite windows, the tops of which were 16 feet above
the floor-level, and 14 beds on a side. The ceiling was arched,
20 feet high in the centre, and averaged a height of about 18
feet, without any obstructing cornices. The floor-space of the
beds was 88»65 square feet, and the cubic space per bed 1629
feet. The fresh air was admitted warmed at a temperature
of 90° by openings i foot square each, under each window,
just above the floor-level, 14 openings in all, and the vitiated
air was extracted by live openings, each ^x6 feet in the
length of the ward in the centre of the ceiling. The hourly
supply per bed was 9000 cubic feet. The high temperature
of the inflowing air caused it to enter with velocity. This
velocity was soon lost. There was an upward movement of
air throughout the ward, but a comparative stagnation in the
centre, for a height of about 8 feet from the floor-level — and
also a comparative stagnation commencing over the bed-heads
and extending to the upper part of the ward, as shown in the
diagram. The respiratory impurity, as shown by excess of
COji over outer air, at the lower level was '00131, and at the
upper part '00240 — thus showing, that with this construc-
tion of ward and system of ventilation, there was a want of
adequate circulation of air, as well as a disadvantage in the
height above the top of the windows, which were 14 feet in
height ; openings at the sides higher up would have per-
mitted the foul air to escape more rapidly from the room,
instead of occupying the waste space above that level at the
risk of cooling and falling again and remixing with the air of
the room. This example shows that extraction-shafts should
be so placed as to cause a circulation of air such as is effected
138 Ventilation combined with Warmed Air
Temperature.
External Air 33° Fahr.
Air Entering 91° to 93°.
at Floor 67°
„ at Head of bed 68^.
„ at Ceiling 75^.
,, at Ventilating Chamber
81 -6.
B.
C.
Hot water pipes to warm in-
flowing Air.
Inlets for inflowing Air.
Outlet for Vitiated Air.
Velocity in feet per second.
The shade shows the appar-
ent course of the Fresh Air.
Fig. 27. Experiment in a hospital ward at Boston, U. S., by Professor E. Wood
of Harvard University,
in Rooms without Open Fireplaces. 139
by a fireplace, which acts to cause a circulation, and to extract
the air. In England the system is often resorted to in asylums
and large houses, of warming the air, and supplying the warmed
air by flues to different parts of the building ; this should be
combined with some plan for the extraction of the vitiated air.
The method of warming rooms by close stoves or by hot
water pipes in the room, do not of themselves necessarily
entail any change of air.
In Germany and the northern parts of Europe, where close
stoves are used, the stove is generally filled with fuel once
a day at an opening often outside the room, and no removal
of air takes place by means of the stove. Therefore, where
there are no special means for changing the air, the rooms
become close and unhealthy ; but in very cold weather, when
there is a great difference between the temperature indoors
and out, a considerable change of air is effected through
crevices of doors and windows, and through every available
aperture ; moreover a spontaneous change of air will take
place through the walls, when the inside temperature greatly
exceeds that out of doors.
Dr. Bohm (than whom no one has better studied ventila-
tion) has adopted for some years the following system in the
Rudolf Hospital at Vienna, where the wards are heated by
close stoves. He there warms fresh air by means of passages
constructed in the fire-clay stoves, placed within the ward, and
the fresh warmed air passes into the ward from the top of the
stove. He provides flues of a large size, and proportioned to
the size of the ward, carried from the level of the ward floor
to above the roof, inside which the flue from the stove is
carried, and in cold weather the difference of temperature
between the air in the flue and the outer air causes a suf-
ficient current in these flues to ventilate adequately the ward.
By this means the fresh warmed air, instead of passing off
to the upper part of the ward, and thence away by flues,
is made to circulate towards the floor of the ward, thus
140 Ventilation combined with Warmed Air
bringing into action one of the conditions of the open fire-
place ; each ward is self-contained in respect of its warming
and ventilation, as is the case when an open fireplace is
used. This is for winter ventilation.
In warm weather, when the stove is not in use, an outlet
into the extraction-shaft is opened by means of a valve near
the ceiling, so as to allow of the escape of the air from the
upper part of the room, in the manner already mentioned ;
the flues in the stove remain as inlets, and other inlets direct
from the open air are also provided at the floor-level and
elsewhere, and the windows can be opened if desired.
There have been numerous close stoves invented of late years
to supply fresh warmed air ; in France the system of hot air
stoves prevails extensively, and it is being gradually adopted
in this country. These provide for the admission of fresh air ;
but care is not always taken to provide both for the removal
of the vitiated air and the supply of fresh air ; and without
provision for both good ventilation is impossible.
In this climate sufficient ventilation can generally be
obtained in private houses, in hospital wards, in barrack-
rooms, and in workhouses, when the proportion of floor-space
allotted to each occupant is comparatively large, by providing
extraction flues and inlets as already described for the pur-
pose of taking advantage of the difference between the tem-
perature indoors and the temperature outside, and by a
judicious use of open windows. But in prisons, asylums, and
buildings occupied by persons under strict rule, as well as in
buildings where large numbers are congregated together for
a limited time, such as theatres, churches, legislative assem-
blies, public meetings, crowded dining rooms or smoking
rooms, and otherwise, cidequate ventilation can as a rule
only be secured by the adoption of some means for extract-
ing the air, beyond that which would be provided by the
simple form of outlet and inlet above described.
This may arise from various causes. For instance, in densely
in Rooms witkouf Open Fireplaces. 141
occupied buildings, where the volume of air to be removed is
large, and the building complicated in shape, dependence on
the difference of temperature and the action of the atmosphere
alone might require inlets and outlets of an inconvenient size,
and therefore some power of extraction to accelerate the
current is necessary. There are also many other cases in
which it is necessary to resort to mechanical means for
changing the air. In all such cases, ventilation must be com-
bined with warming, on the score of convenience as well as
of economy.
In hot climates the conditions differ materially from those
already alluded to. The difference of temperature indoors and
out is rarely sufficient to produce an adequate change of air.
The object to be attained is the reverse of that sought in this
climate. The fresh air to be supplied should be cooled down
below its outside temperature instead of being raised above it.
In hot climates it will therefore generally be necessary to
provide some artificial means of removing the air, in order
to secure an adequate change of air in rooms or halls occupied
by many people.
Ventilation by mechanical means may be effected either by
propulsion or by extraction. By propulsion fresh air would
be forced into the building to drive out the vitiated air. To
effect this, Dr. Arnott proposed an apparatus on the principle
of the gas-holder, by which he could carefully regulate the
quantity of inflowing air. In the House of Commons there
is an apparatus on the principle of a large pump, for oc-
casional use, by which in the summer a given quantity of
cooled air can be forced into the House. At the Hospital
Necker at Paris, fans were used for forcing a given quantity
of air into the wards.
It is probable that a system of propulsion might be found
to be the more convenient system for freshening the air in
rooms in hot climates, combined with openings in the upper
part of the room. The air might be compressed in the course
142 Ventilation combined with Warmed Air
of the propulsion in impervious underground channels, in
which it would be retained sufficiently long to be cooled down
by the lower underground temperature, and in passing into
the rooms or wards it would be still further cooled down by
the expansion. In towns where the subsoil is liable to be
very polluted greater care must be exercised to prevent the
ground air from mixing with the air for ventilation.
But, as has been already observed, experience shows that a
system of propulsion has not acted satisfactorily in hospitals
in this climate, unless it has been combined with a system for
the extraction of the vitiated air. And under ordinary cir-
cumstances, where extraction is resorted to, an adequate
quantity of fresh air can be drawn in by the operation of
the extraction-shafts, without the additional expense and
trouble of propulsicJn.
In the case of ventilation by extraction, it is generally
found convenient and economical to provide one principal
extraction-shaft, to which the extraction-flues from the sepa-
rate apartments are brought; and to warm the fresh air at
some central apparatus before it is drawn into the rooms.
The effect to be sought for in a room from the use of
extraction-shafts is as follows : —
Currents created by outlets placed near the floor-level and
led into extraction-shafts must be arranged to move only at a
low velocity into the outlet, in order to prevent draughts : the
temperature of air as it enters the outlet is not affected, as is
the case with the open fireplaces ; therefore the tendency to
create a circulation of air in the room does not prevail to the
same extent as with an open fireplace ; and if a room with-
out an open fireplace is to be equally efficiently ventilated by
extraction-shafts alone, the advantages which an open fire
presents must be compensated for by placing the outlets and
inlets in such positions and in such numbers as will prevent
stagnation of air in any part of the room. In cold weather
the extraction should generally take place from the lower
in Rooms without Open Fireplaces, 143
part of the room, so as to draw off the cold air from near
the floor, and cause the warm air above to circulate.
In this case the orifices for extracting the air should be
raised above the floor sufficiently to prevent dirt falling into
them, and it is advisable if possible not to place them near
the feet of persons sitting down in the room, because the con-
tinual flow of air, even at a low velocity, produces an evapora-
tion which in time may create a feeling of cold. It may be
generally said that the larger the area through which the air is
drawn off the less will any unpleasant effects be experienced.
Thus in a lecture-room the vertical risers of the seats may
be advantageously made entirely of open grating, so that the
whole area is available for drawing off the air.
On the other hand, in rooms with many occupants, where
much gas is used, in hospital wards, in smoking rooms and
dining rooms, or other places under similar conditions of the
vitiation of air, the heated air at the top of the room should
be rapidly removed by special outlets near or in the ceiling,
in addition to extraction at the floor-level ; care being taken
that both sets of outlets shall draw efficiently. The heat
which results from gas affords of itself a means of extrac-
tion, if judiciously applied.
The supply of fresh air should be placed above the heads
of the occupants of the room, and admitted through inlets
sufficiently far from the extracting outlets to prevent its being
carried away at once.
The construction of the large cathedrals lends itself to
ventilation ; because the lofty nave with clerestory windows,
and the towers, are convenient means for the removal and
admission of air, and if the windows were all opened after a
service, very little inconvenience would be experienced even
from the largest congregation. But there are many churches
in this country where large congregations are crowded into
buildings of inadequate size and height, and these require
special care.
144 Ventilation combifted with Warmed Air
In churches with galleries, densely occupied, and in halls
for meetings, the air should be drawn off from the top as well
as from below. The upper air, in cases of crowded meetings,
is filled with much moisture from the breath ; it is therefore
advantageous to warm the air thus drawn off as it enters the
extraction-shafts, in order to increase its capacity for mois-
ture, so that the moisture shall not be deposited before it
passes into the outer air.
Theatres present peculiar difficulties of ventilation, from
their • complex arrangement. The entrance, staircases, and
corridors should be warmed independently of the part oc-
cupied by spectators. These require but little ventilation.
The part occupied by spectators is under different conditions
when the curtain is down and when it is raised ; therefore the
stage should be warmed and ventilated independently of the
part reserved for spectators. As the latter part requires a
large amount of light, and as light is inseparable from heat,
the light should be utilised for promoting ventilation. The
heated air should be drawn off above, and the fresh air duly
warmed in winter should be admitted at levels on which
spectators are placed, without draughts. Adequate venti-
lation in a theatre will, as a rule, be more satisfactory, if some
mechanical appliance be provided to force in the fresh air as
well as to remove the vitiated air. In summer the ventilation
requires to be modified so as to supply air cooled either by
compression or otherwise, as may be found most advanta-
geous. The effectual ventilation of a theatre requires the
presence of a special attendant to watch continuously the
condition of the air in the theatre, and modify the arrange-
ments from time to time.
The object of this treatise is not to define closely special
methods of ventilation; but rather to bring into view the
principles which should guide the architect or engineer in
considering the system most applicable to the requirements of
his particular case ; because the enunciation of specific rules
in Rooms without Open Fireplaces. 145
in so complex a subject might fetter him and prevent advance-
ment in sanitary science.
The following instances of some of the systems of ventila-
tion which have been adopted in various buildings will afford
a general idea of the principal points which have to be con-
sidered.
The old Roman plan, by which the source of warmth was
uniformly distributed by heating the floor and walls of a
room, gave an equable temperature; and by warming the
floor and walls rather than the air partially provided one of
the advantages arising from the open fire.
If in connection with this system fresh cold air were ad-
mitted near the ceiling, and if the warmed vitiated air were
removed by outlets near the ceiling, and if each occupant had
a sufficient floor space, it is probable that this would form a
very comfortable arrangement.
The Roman floor was a floor of tiles laid hollow with flues
underneath. The furnace was formed at one end, and the
smoke from the furnace was carried backwards and forwards
along the flues under the floor, and finally led up the walls or
to a chimney. This chimney was generally so placed as to
act as a means of keeping the store of wood dry.
But such a plan could only be adopted in a specially
constructed building. It would not be convenient in ordinary
houses.
An experiment was made to compare the economical effect
of warming by means of a heated floor with the effect of heat-
ing by means of a ventilating fireplace; the experiment lasted,
with each mode of warming, for two days. It showed that, in
the case of the warmed floor, the room was maintained at a
temperature of about 18 degrees above the temperature of the
outer air with an expenditure of 56 lbs. of coal and iialbs. of
coke, whilst with the ventilating fireplace the expenditure was
only 75 lbs. of coal ; the cost being 3^. 4^. for the warmed floor
as compared with i^. 4^. for the ventilating fireplace. It is
L
146 VepJilatton combined with Wanned Air
probable however that in a house designed and constructed'
specially for this mode of heating, better results would have
been obtained.
The ventilation of Derby Infirmary, designed and carried
out more than sixty years ago is an instance of ventilation
by natural extraction and propulsion alone.
Flues were led from each ward to a central shaft, at the top
of which was placed a cap with a vane arranged so as always
to cause the opening to face away from the wind. Fresh
air was introduced by means of another shaft, also furnished
with a cap with a vane arranged to make the opening
always turn towards the wind like a wind-sail in a ship. The
fresh air entering this latter shaft was carried down under-
ground along a channel 70 feet long to an iron stove covered
with flanges, where it was heated in cold weather ; and thence
it passed up by separate flues to the wards. The extraction-
flues were led from apertures near the ceiling, and the wards
were also provided with open fireplaces near the floor-level.
Thus the action of the wind was employed to extract the
vitiated and to propel the fresh air. The amount of air
which was thus passed through the wards with a velocity of
wind of about 3 miles per hour, was recorded as 400,000
cubic feet per hour. But of course on perfectly calm days the
effect of the extraction-shaft was limited to the extraction
force resulting from the diflference of temperature and the
height of the shaft; this force was necessarily much modified
by the friction from the length of the flues in addition to the
delays caused by the horizontal portions of the flues. Straight
flues carried up separately from each vvard would have been
more efficient for extraction. The underground channel had
the effect of partially warming the fresh air in winter and
cooling It in summer.^
The Great Opera at Vienna is ventilated by extraction-
* This system was invented by G. W. Sylvester and William Strutt, but recent
alterations have abolished it.
in Rooms without Open Fireplaces. 147
shafts carried from round the ceiling, from above the central
chandelier and from the upper part of the boxes and galleries.
These are brought into action by the heat generated by hot
water boiliers and by the products of the gas chandelier ; the
admission of air is regulated by propulsion by a fan from
below. The air thus supplied is partly passed over pipes
heated by hot water in winter, and is partly left cold.
Channels for hot air and channels for cold air are provided
to all parts of the theatre, under each occupant of the pit
and stalls, and in the corridors for the supply of the boxes,
in addition to a large volume of air admitted near the stagey
so as to keep the ventilation for the spectators separate from
that for the actors. In hot weather the ait can be cooled by
being passed through spray, tn order to nlaintain the venti-
lation in efficient action, metal thermometers are placed in
different parts of the theatre, all connecting by electric wires
with a small office in the basement, and these indicate the
temperature in different parts of the building at each moment
on a board in the office. When the observer sees that the tem-
perature is raised or falls unduly, in any part of the house, he
can open or close valves, which are under his hand, and which
regulate the quantity of warm or cool air admitted to each part
of the house, and thus alter the temperature as desired.
The New Opera at Paris is warmed by hot water apparatus
for all the parts behind the stage, on the assumption that this
method does not dry the air so much, whilst the part of the
theatre occupied by the public is warmed by stoves, as being
more rapidly put in action.
The fresh air is introduced through flues in the floor of the
several tiers of boxes, and the vitiated air is extracted partly
from the back of the boxes and partly from the floor of the
pit and stalls. The heat from the lights is not applied to
ventilation.
Figure 38, on the next page, shows the system in use in the
Houses of Parliament.
L %
148 Ventilation combined with Warmed Air
Fig. 28. Venlilalion of the Housi! of Commons.
in Rooms without Open Fireplaces, 149
The Houses of Parliament are warmed and ventilated by a
combined arrangement. For the House of Lords and the
House of Commons the arrangements are identical.
The fresh air is admitted into a lower chamber, where it
is warmed by pipes. Through these pipes steam circulates ;
broad vertical flanges are cast at intervals on the pipes
in order to increase the heating surface. Each of these
flanged portions of pipes has therefore a similar heating
power. The frequent alteration in the number of occupants
of the House of Commons makes it necessary frequently to
alter the temperature of the air. This alteration is effected
by an assistant, who watches the thermometer and covers with
pieces of woollen fabric, or uncovers, a greater or less number
of these flanged portions of the pipes, so as to diminish or
increase the heating surface as may be required.
The fresh air is supplied to this chamber from the adjacent
courtyards, which are covered with asphalte and kept tolerably
xlean*
The air, after having been warmed in the lower chamber, is
«
passed through four large circular openings of about three feet
six inches diameter each, into a chamber above : this chamber
is practically a portion of the House of Commons, and is
separated from it only by means of an iron grated floor
covered with open matting. ' The grated floor and the grated
risers of the steps on which the seats are placed are all avail-
able as inlets. The glass ceiling of fhe House of Commons
has openings into the space in the roof, from which a channel
leads down under the basement to the foot of the clock-tower,
where a large fire is maintained ; and this forms the exhaust
by which the air is drawn through the house ; as much as
1,500,000 cubic feet have been passed through per hour. If
the house were full, this would represent somewhat under
aoGO cubic feet per occupant per hour, including members,
attendants, and strangers. The lighting is effected by gas-
lights placed above the glazed ceiling.
150 Ventilation combined with Warmed Air
In summer an arrangement has been adopted, by which air,
made cool by passing over ice, has been forced into the house.
This is an expensive process for cooling the air. Equally
good results at a much less cost might be obtained by utilis-
ing the underground temperature in summer, or by using
compressed air. The air is drawn from the ground-level,
which is an undesirable arrangement. Much purer air could
be obtained by bringing the air down from the lofty towers
which form part of the structure.
The French Legislative Chambers were ventilated by
General Morin on a plai> the reverse of that adopted in the
Houses of Parliament. The Legislative Chamber has a cubic
content of about 400,000 cubic feet ; the arrangements are
intended to provide for 1,060,000 cubic f^et of air to pass
through the chamber in an hour. The air is extracted
through openings at the floor-level, and others placed in the
vertical risers under the seats, in the body of the hall and in
the galleries ; there are also outlets in the staircases and
corridors of approach. The united area of the extracting
outlets is nearly 160 square feet, which would allow of a
velocity of i-8 feet per second in supplying the regulated
quantity of air.
The air is admitted at the ceiling-level through openings in
the cornice all round the chamber and in the capitals of the
columns. The total area of inlet is about 195 square feet,
which would allow of a velocity of about i«.5 feet per second
for the inflowing air, with the maximum supply, which how-
ever is rarely attained.
The fresh air is brought down by a flue from a height of 60
metres into a chamber at its base, where it is warmed to the
necessary temperature by four (or fewer) stoves of brick
provided with air-passages. The adjacent committee-rooms,
and the rooms and corridors for the use of members, are
warmed and ventilated in connection with the chamber, or on
the same principle — the total amount of air being 1,600,000
in Rooms without Open Fireplaces.
n^
Cubic feet per hour. The difficulty of maintaining a uniform
temperature in the chamber arises from the continual varia-
tion in the number of occupants. The temperature main-
tained in the winter is about 64^° Fahrenheit, with a variation
seldom exceeding 3° or 4°. In spring, with an outside tem-
perature of 57°, the inside temperature has rarely varied
Fig. 29. Sir Joshua Jebb*s system of Ventilation for Prisons.
more than from 64® to 68°. In summer, with an external
temperature of 82°, a temperature has been maintained in
the chamber of from 73° to 77°.
The air being brought first into the vaults below the ground,
its temperature is raised to begin with by the temperature
152 Ventilation combined with Warmed Air
of the vaults ; in winter as much as from 9° to 13° above the
outside air; in summer it could be cooled down as much
as from 16° to 18° below the outer air, but this would be
beyond what would be endurable in practice.
The temperature in the main extraction-shaft averages from
36° to 45° above that of the outer air ; but in summer, with
an out-door temperature of 83°, it was found necessary to
raise that of the main extraction-shaft to about 142°, or a
difference of 59°. Experiments were made to ascertain
whether, in order to gool down the chamber in the great
summer heats, it was desirable to continue the ventilation
through the night, but the results did not correspond with the
extra expense.
The system of ventilation of cells in prisons adopted by
Sir Joshua Jebb was practically the same as the system
originally proposed by Sylvester and General Morin, viz. the
extraction of the air at the lower part
of the cell and its admission near the
ceiling (Fig. 29). In cold weather this
t method of admitting the warmed air
1 keeps the temperature of the cell uni-
form. When the extraction- current is
sluggish, as may be the case in warm
weather unless much extra fire is used,
this plan of removing the air from below
does not always sufficiently relieve the
cell unless the window is opened. A
, better effect will be produced by the
1 removal of air from the upper part of
the cell. The most convenient arrange-
ment would be to have a shaft as shown
in the diagram (Fig. 30), with an opening
■S' l°- tQ be closed alternately either at the top
or the bottom according to the weather. In lai^e prisons the
most economical arrangement is to warm the fresh air at some
in Rooms without Open Fireplaces. 153
central source of heat and distribute it thence over the build-
ing. The extraction must either be mechanical, or by means of
a heated shaft, because these prisons have large central halls
into which the cells all open, and which would disturb the ven-
tilation in the absence of mechanical extraction. Care should be
taken that the flue from each cell shall have a sufficient length
before it enters the main extraction-shaft, to ensure that there
are no reverse currents, for these would bring impure air back
into the cells. This arrangement requires that the fire for the
extraction be kept up day and night. For cells on one floor,
such as barrack or police cells, where the number is small, the
simplest and most efficient arrangement is to provide a small
shaft for each cell direct to the open air, with an opening near
the floor for winter and near the ceiling for summer, one valve
being arranged to be closed when the other is open, the cells in
this case being warmed by hot-water pipes in coils, or flanged
pipes, behind which fresh air is admitted into the cell so as to
come in warmed when the pipes are in use. Direct openings
from such cells into a general extraction-shaft carried along
the ceiling of the several cells are objectionable, because under
such an arrangement the impure air from one cell frequently
passes into the adjacent cells. If such a general extraction-
shaft be provided, the least dangerous plan would be to place
it at .a height of at least 6 feet above tlie ceiling of the cells;
and to carry a small shaft from each cell vertically up for a
few feet in length into it ; a current being maintained by
mechanical means, or by heat in the shaft.
In the Herbert Hospital the warming of the wards is
eff*ected by open fireplaces, whilst the subsidiary accom-
modation is warmed by hot-water pipes. The administrative
offices are in a separate building from those which contain
the sick.
The wards are on the pavilion principle, with windows on
opposite sides, the beds being placed between the windows.
Each ward has its nurses' room and ward-scullery at one
154 Ventilation combined with Warmed Air
end, and its ablution- and bath-room and water-closets at the
other. Every water-closet has a separate window, and the
ventilation of these ward offices is most carefully cut off from
that of the wards themselves. The walls are built hollow,
and the windows are glazed with plate-glass, to save the heat,
which the large extent of wall and window surface would
otherwise allow to escape. The ward walls are of parian
cement, the ward floors of oak, to be kept polished with
beeswax. The ventilation of all the wards is as fol-
lows :—
First the windows open at top and bottom on both sides,
then shafts, 14 by 14, pass up at each corner of the ward, to
above the roof, to allow of the escape of foul air. Sherring-
ham's ventilators are placed in each wall-space, between the
windows, to admit fresh air when the windows are closed.
For cold weather the principal engine of ventilation is the
fireplace. There are two in each ward, placed in the centre
line of the wards. The flue passes horizontally under the
floor to a vertical flue in the wall. Fresh air is admitted by
the side of the horizontal flue, through openings in the fire-
clay sides of the fireplace, into the ward, by which means it
becomes warmed ; so that each fireplace, when the fire is
lighted, pours a continuous supply of fresh warmed air into
the ward, and a great portion of the heat, which would other-
wise pass into the chimney, is saved. The ablution-rooms
and water-closets, as well as the lobbies which separate the
ablution-rooms and water-closets from the wards, are each
warmed by a separate service of coils heated by hot water
from central boilers, and ventilated by fresh air admitted
through the coils of these hot-water pipes. The vitiated air
escapes by means of a separate shaft carried up through the
roof from each ablution-room, water-closet, and lobby. The
staircases, as well as the corridors separating the pavilions, are
each warmed independently by hot-water coils, and ventilated
by fresh air admitted through the coils. Each part of the hos*
in Rooms without Open Fireplaces. 155
pital is thus independent of every other part for warming and
ventilation.
These instances sufficiently elucidate the general principles
affecting combined warming and ventilation.
In all systems in which the walls derive their heat from the
air of the room only they are necessarily somewhat colder
than the air of the room. It has been mentioned that one of
the main causes of the comfort of the open fireplace is that
with it the air of the room derives its warmth from the walls
which are warmed by the rays of the fire, and therefore that
the walls are at least of the same temperature as the air ;
stoves and hot-water and steam pipes in a room also radiate
^ portion of their heat to the walls, those heated to a low
temperature less effectively than those heated to a high
temperature. Heating effected by warmed air can only be
thoroughly comfortable when its use is combined with some
plc^n of warming the floors, walls, and ceiling, so that their
temperature may not be dependent on that of the air after it
has entered the room.
In conclusion, no system of ventilation and warming in a
large building or establishment can be satisfactorily conducted
unless some person is charged with the duty of seeing that it
is maintained at all times in effective action, on the principle
of that adopted at the Opera in Vienna.
CHAPTER XIII.
CONDITIONS AFt'ECTING THE INTERNAL ARRANGEMENTS
OF BUILDINGS.
The laws regulating the movement of air should govern the
form of buildings.
Plans for houses, barracks, asylums, schools, and hospitals
necessarily vary either with the wants of the individual or
with public requirements, with the site, the aspect, and the
cost. It is therefore impossible to do moire than sum up the
general principles which should be observed in a design. 'But
in both private and public buildings arcliitects should conform
their architectural design to the internal requirements, and
not, as is too often the case, make the internal arrangements
conform to the design of the fa§ade.
Fire-proof buildings are desirable; a planter covering to
woodwork is a very good protection against fire. In the
Communist riots in Taris, wood covered with plaster was
charred, not consumed.
Fires frequently spread with rapidity in English houses
because currents of air generated by a fire are enabled to pass
up from one -floor to another behind the boding of windows,
the battening on walls, the lath and plaster partitions, &c.
The free passage of air-currents should be stopped between
every room and the room under it and over it, by means of
some substance difficult of combustion. There should also be
a course of fire-clay slabs (Fig. 31), projecting at least
lolid Ebb of Fii
Fig. 31-
The Internal Arrangements of Buildings. 157
6 inches all round the walla of a room to receive the beams
of the floor above, and against which the plaster ceiling
should abut. Such arrangements
would greatly check the passage of
fire from story to story in a house.
There should invariably be circu-
lation of air round every building.
Back-to-back dwellings, as well as
houses and cottages built with in-
terlocking walls, are inadmissible, for
reasons already explained.
Dwellings should not be built over
stables, because it is impossible to keep the air of a stable
as pure as that of a living-room ; nor should dwellings be
placed over stores or shops, where matters liable to putrefy
are kept.
To guard against the liability of impurity in the ground on
which the house is built, when danger is apprehended from the
presence of decaying organic matter, the most healthy plan
would be to build the house over an arched floor raised above
the ground-level, the space under the floor being open to the
air on all sides.
Basements are sometimes used in towns as dwellings : they
are undesirable. There should always be an area between
the basement and the street in houses situated in towns, to
prevent emanations passing into the houses through the earth
from defective gas-mains and sewers. Where cellars are pro-
vided undei^ound, means should be taken to cut them off
from the ground-air.
Pure, dry air of the required temperature should pervade,
every part of a dwelling. The, form of the interior of a
dwelling should be such as to ensure this, and at the satne
time prevent stagnation of air. In cold and temperate climates
when the weather is warm, and in hot climates always, change
of air largely depends on open windows and doors ; conse-
158
Conditions affecting
quently the relative position of windows and doors should be
selected so as to enable the air of a room to be thoroughly
changed when they are opened.
Lofty rooms are advisable, because the height facilitates the
change of air without draught, provided the windows or other
means of outlet for air be arranged so -as to prevent stagnation
near the ceiling, and so that impure and heated air which has
risen to the upper part of the room may be removed rapidly.
If time be afforded for its cooling, the impurities will fall and
mix again with the air of the room. A lofty room, if warmed
and provided with adequate means of change of air at the
upper part, is more comfortable and healthy than a low room.
In new houses or cottages, a height of ten feet should be the
minimum height for the best rooms, and no room in a cottage
should be under an average of eight feet high.
An abundance of light, and in this country direct sunshine,
is always necessary for maintaining purity of air. In a hot
climate means must exist for intercepting the direct rays of
the sun.
A dark house is an unhealthy house, an ill-aired house,
and a dirty house. Therefore light should penetrate to every
part. There should be no dark
staircases, corridors, corners, or
closets. Direct light by means
of windows easily opened to
the outer air is required to
ensure the frequent renewal of
the air. Staircases, if lighted
by skylights, should have the
skylights made of the lantern
form, with side-lights to admit
fresh air without admitting rain.
A hall or staircase in the centre of a house, carried up the
whole height of the building, with light and ample ventilation
by large windows at the top, forms a reservoir of air which
Fig. 32.
the Internal Arrangements of Buildings. 159
may be kept fresh, and which materially assists in keeping
pure the air of a house.
Every room in a building should have access to light and
air, by means of a window in an outside wall. The rooms
appropriated to removal of refuse, such as housemaid's closets,
and water-closets, require more light, and therefore propor-
tionately larger windows, than other rooms. Store-closets
should also have direct access to fresh air.
The larger the proportion which the area of surface occupied
by a house bears to the number of occupants the better.
In towns where land is dear, and where a large number of
persons are crowded on a given area, better ventilation and cir-
culation of air may be obtained by placing dwellings on stories
one above the other, and leaving spaces between the buildings,
instead of in one-storied buildings which would be too close
together to allow of circulation of air round the building.
Under these circumstances, the height of a dwelling must
be regulated with respect to its surroundings. That is to say,
in the case of ordinary dwellings adjacent to each other, the
distance apart of the dwellings should at least equal the
height of the dwelling, so as to ensure adequate light and air
in the lower floors. These considerations limit the number of
stories in houses of the better classes in towns, or of an aggre-
gation of cottages, each with its separate family, such as is
created by a model lodging-house, where the arrangements
prevent a community of air throughout the building.
Basements should never be used for sleeping- rooms, nor
indeed for human dwellings. They are always more or less
liable to damp, stagnation of air, and deficiency of sunlight,
and are well-known nurseries of disease.
The number of stories in the case of barracks, workhouses,
asj'lums, schools, and hospitals, where the conditions of the
occupation entail a community of air throughout the building,
must be more closely limited.
i6o Condilions affecting
The following conditions afford a general idea of the con-
siderations which affect these buildings.
In all such buildings, where a large number of human
beings are to be lodged together, it is especially advisable,
as a general principle, not to place anything which might
injuriously affect the purity of the air in the same building
with the inhabitants.
Kitchens, latrines, ablution-rooms, and baths, should there-
fore as far as possible be built away from them.
Buildings should be arranged in the simplest manner.
Squares with closed angles should be as far as possible
avoided. The great object to be aimed at is to have free
external ventilation all round the buildings ; in temperate and
cold climates to have as much sunlight as possible, and to
avoid a purely northern exposure for living-rooms. These
conditions are essential to health. Free access of sunlight to
a square is best obtained by placing two opposite angles of
the square north and south.
If the administrative conditions allow of it, the simplest
arrangement for such buildings is in a single line, lying north
and south if possible, to allow the sun to shine on both sides
of the range every day. The line may be divided into separate
blocks for facility of passing across it at different points.
No part of any asylum, workhouse or barrack, whether for
sick or healthy men, should be placed close to the boundary
walls. There should be always intervening space sufficient to
ensure thorough ventilation round the buildings between them
and the wall, and to prevent the ventilation from being
injuriously affected by buildings belonging to the adjacent
population placed close" to the walls. Latrines, cook-houses,
stores, and other similar buildings, can be placed between the
building and the wall, but the arrangement should be such as
not to interfere with the external ventilation of the building.
All populous buildings where there is an intercommunity of
air throughout the building, such as barracks, schools, work-
the Internal Arrangefnents of Buildings, i6i
houses, and asylums, are best constructed of only two stories
of living-rooms. Three stories are not objectionable for healthy
people, though very undesirable for sick. Four stories should
only be resorted to when, from restricted dimensions or from
the form of the ground, it is absolutely necessary to adopt this
number of floors.
- Rooms for dry stores or for administration, or rooms occa-
sionally occupied, such as libraries and reading-rooms, may be
placed without detriment on the ground-floor, the sleeping-
rooms being placed over them, when necessary. Barracks and
hospitals have this in common, viz. that the sleeping-rooms
are mainly also living-rooms ; they differ in this respect from
asylums, schools, and workhouses. The following rule should
apply uniformly to all buildings of the nature of an asylum,
barrack, hospital, and workhouse, viz. such buildings should
be subdivided into separate houses, without direct communi-
cation between the adjoining houses. To ensure this, the party
walls between the houses should be carried above the roof.
Each house should further be divided up the middle by
a wide roomy staircase, extending from the ground to the top
floor, with a free ventilation through the roof. The staircase
and passages should extend across the house from front to
back, with windows on opposite sides for through light and
ventilation. Besides affording means of access, the stairs and
passages should be so constructed as to afford ventilation
upwards between the two halves of the house, suflScient to
prevent the atmosphere in rooms on opposite sides of the stair-
case and passages from intermingling.
There should be a unit of size for all asylums, workhouses,
and barrack-rooms, containing the principal rooms and theii"
appurtenances, so that a building of any size, which has a
definite object, may be constructed by simply increasing the
number of such units.
The unit of construction for workhouses and asylums has
not been laid down by any distinct authority; for barracks
M
1 62 Conditions affecting
and hospitals the conditions have been laid down by the
Barrack and Hospital Improvement Commission ; and for
prisons they have been stated by the late Sir J. Jebb.
The unit of construction for a school necessarily depends
upon the nature of the school, and the number of classes into
which it is divided.
These conditions vary in almost every case. It may how-
ever be assumed, that for school-rooms or lecture-rooms
which are occupied for limited periods in the day-time, and
thoroughly purified between times, a superficial area per
pupil in the class-room of from 15 to 20 feet as a minimum,
should be afforded, and a cubic space of not less than from
180 to 250 cubic feet. This, at 1200 cubic feet per hour per
occupant, would imply a renewal of the air of the room from
5 to 7 times in the hour. But for a schoolroom occupied for
limited periods, the windows being opened between times, 750
cubic feet per hour per occupant during school hours would
probably suffice ; reckoning after dark each candle as an occu-
pant, and each gaslight as two candles. Windows in rooms
where drawing or writing is carried on are best placed so as
to be on the left hand of the student.
The conditions of school dormitories would follow those in
barracks and workhouse wards which have been already
alluded to in a previous chapter.
A short account of how the unit of accommodation far
barracks and hospitals was arrived at will best explain the
application of the general principles to special cases.
For barracks, from 20 to 30 beds was fixed as a convenient
unit of number for each barrack-room, the beds being arranged
v^ ith their heads to the walls on opposite sides of the room.
There should be about half as many windows as there are
beds in the room ; they should be on opposite sides of the
room ; they should be carried up to within a few inches of the
ceiling, and be hung so that both upper and lower sashes can
be opened or shut.
the Internal Arrangements of Buildings. 163
In no case should there be more than two rows of beds
between the opposite windows. This rule holds good in all
climates, but more especially in hot climates.
Assuming a fixed floor-space, the width of the room must
be such as to secure an adequate distance between the beds.
There is a minimum limit of width which depends on the
question of convenience. Nineteen or twenty feet would be a
good width for a barrack^room in this climate, but in hot
climates a larger floor-space would be required, which entails
additional width and length. The width above mentioned
would allow space for tables and forms when the beds are
down, and would allow about 11 or 12 feet between the oppo-
site beds during the day when the bedsteads are turned up.
Barrack-rooms should never be less than la feet high.
A room 20 feet wide and la feet high, with 5-feet bed-
spaces along the walls, would give the regulation amount of
600 cubic feet per bed. If the height of the room is less than
I a feet, it would be better to make up the unit of cubic space
by increasing the bed-space along the walls, rather than by
increasing the width of the room.
All sleeping-rooms should have ceilings. The space in the
slope of the roof should not be taken into barrack-rooms any
more than into the rooms of ordinary dwelling-houses. That
space if in the room should always be ventilated ; otherwise it
affords facilities for the impure air to stagnate, cool, and remix
with the air of the room.
The fireplace should be placed in the side wall in the
centre of the length of one side of the room, and should be
constructed to warm part of the air admitted for ventilation^
If the room were constructed for 30 beds, two fireplaces
would probably be required ; in which case they should be
placed on the same side of the room, to diminish the proba-
bility of their smoking, and to assist ventilation.
Each barrack-room should have a room for a non-com-
missioned officer opening from the landing or passage, and
M 1
164 Conditions affecting
connected with the barrack-room ; and either at the entrance,
or at the further end opposite the entrance, there should be
a well-lighted and well-ventilated room, with ablution-basins,
and a bath. There should be in addition a water-closet and
urinal for night use, with windows to the outer air.
Hospitals require especial care, because the sick are more
easily affected by insanitary conditions than persons in health.
The unit of hospital construction is the ward, with its ward
offices.
The area of the ward depends on the floor-space allotted to
the patients, to which allusion has already been made, and
varies with the climate, and with the object of the hospital.
The breadth of the ward to some extent regulates the other
dimensions. It is essential that the windows should be oppo-
site, and, in order that they may act efficiently for changing
the air, that they shall not be too great a distance apart. The
breadth which combines convenience with this condition is
from 24 to 28 feet, but 30 feet would not be too wide. With
this form of ward, the beds would stand between the windows.
The ward offices are of two kinds.
1. Those which are necessary for facilitating the nursing
and administration of the wards, as the nurse's room and
ward scullery.
a. Those which are required for the direct use of the sick,
so as to prevent any unnecessary processes of the patients
taking place in the ward ; as, for instance, the ablution-room,
the bath-room, the water-closets, urinals, and sinks for empty-
ing foul slops. There should, in addition to the bath-room
here mentioned, be a general bathing establishment attached
to every hospital, with hot, cold, vapour, sulphur, medicated,
shower, and douche baths. Separate water-closets are re-
quired for the nursing staff.
Hot and cold water should be laid on to all ward offices in
which the use of either is constantly required, in order to
economise labour in the current working of the hospital.
the Internal A rrangemenls of Buildings. 165
The nurse^s room should be sufficiently large to contain a
bed, and to be the nurse's sitting-room. It should be light,
airy, and well ventilated. It should be close to the ward door,
and it should have a window looking into the ward.
There should be a ward scullery attached to each ward,
and adjacent or opposite to the nurse's room, so as to be
under her eye.
There should be no dark corners in the scullery, and it
should have ample window-space.
There should be provided, adjacent to the scullery or nurse's
room, well lighted rooms for linen, stores, or patients' clothes,
and a hot closet for airing clean towels and sheets.
The ward offices of the second class ought to be as near as
possible to the ward, but cut off from it by a lobby, with doors
at each end, and windows on each side, and with separate
ventilation and warming, so as to prevent the possibility of
foul air passing from the ward offices into the wards. These
offices are therefore most conveniently placed at the end of
the ward, furthest from the entrance and nurse's room, and
distributed at each side, so as to enable the ward to have an
end window.
The ablution-room should contain a small bath-room with
one fixed bath of copper, supplied with hot and cold water.
A terra-cotta bath when once warmed has the advantage of
retaining the heat longer than a bath of almost any other
material, and of being always cleanly, but it absorbs a great
deal of heat at first. Hence, when the bath is frequently
used, it is the best material ; but if the bath is seldom used,
then copper is better, or polished French metal.
The water-closets should never be placed against an inner
wall, but always against an outer wall of the compartment in
which they are situated, and the soil-pipe should be carried
down outside.
Walls of ablution-rooms and water-closets should be
covered with white glazed tile, slate enamelled or plain, or
1 66 Conditions affecting
Parian cement ; plaster is not a good covering, for them on
account of their liability to be splashed, and of the necessity
for the walls to be frequently washed down.
The ablution-room and water-closets should have plenty of
windows opening to the outer air. They should have shafts
carried up to above the roof, to carry off the foul air, and
ventilated openings to admit fresh air independently of the
windows, and warmed air should be supplied to them inde-
pendently both of the wards and of the lobbies which cut
them off from the wards, which latter should also be carefully
ventilated and warmed separately.
These ward offices will vary but little with the size of the
ward ; that is to say, a ward of twenty beds will require
nearly as large ward offices as a ward of thirty-two beds.
Scale
'-^■■f...f ."> f^ .*> ^ .«> fio .^ .^ ^ ,»oo "
Fig 33.
For instance, three water-closets per ward will suffice for a
ward of thirty-two beds, but two at least will be required for
even a twelve-bed ward. The superficial area to be added in
the wards of thirty-two beds for these appliances would be
about thirty square feet per bed, whereas in wards of twenty
beds each it would come to nearly fifty square feet per bed.
The ward with its ward offices is a small hospital, which
may be increased to any required size by the addition of
similar units.
The principles upon which these units of ward construction.
the hiternal A rrangements of Buildings, 167
or, as they are generally termed, pavilions, should be added,
are as follows : —
I. There should be free circulation of air between the
pavilions.
%, The space between the pavilions should be exposed to
sunshine, and the sunshine should fall on all the windows in
the course of the day, for which purpose it is desirable that
the pavilions should be placed on a north and south line.
3. The distance between adjacent pavilions should not be
less than twice the height of the pavilion reckoned from the
floors of the ground-floor ward. This is the smallest width
between pavilions which will prevent the lower wards from
being gloomy in this climate; and where from local con-
ditions there is not a free movement of air round the buildings
this distance should be increased.
4. The arrangement of the pavilions should be such as
to allow of convenient covered communication between the
wards, without interfering with the light and ventilation ;
and therefore the connection between adjacent pavilions
should be on the ground-floor only, or in the basement, and
the top of the covered corridor uniting the ends of pavilions
should not be carried above the ceiling of the ground-floor
wards. Indeed, whilst it is necessary to make the ground-floor
wards from twelve to fourteen or fifteen feet high, it would be
unnecessary for purposes of communication to give the cor-
ridor a greater height than nine or ten feet ; there is how-
ever this consideration, that if the top of the corridor is made
level with the ward floors of upstairs wards, it affords a
convenient terrace on to which the beds of patients can be
wheeled, so as to allow them to lie in the open air. Each
block of wards — that is, each pavilion — should have its own
staircase.
5. No ward should be so placed as to form a passage-room
to other wards.
6. As a general rule, there should not be more than two
1 68 Conditions affecting
floors of wards in a pavilion. If there are three floors or
more, the distances between the pavilions become very con-
siderable, because of the rule, which ought to be absolutely
observed, of placing the pavilions at a distance apart equal to
at least twice the height of the pavilion, measured from the
floor-level of the ward nearest to the ground. Besides, when
two wards open into a common staircase, there is, with every
care, to some extent a community of ventilation. When
there are as many as four wards one over the other, the stair-
case becomes a powerful shaft for drawing up to its upper
part the impure air of the lower wards, which is then liable to
penetrate into the upper wards. Similarly, heated impure air
from the windows of the lower wards has occasionally a ten-
dency to pass into the windows of the wards above. For
these reasons, no hospital should have more than two floors
of wards, one over the other ; and if there is a basement under
sick wards, it should not be used for' any purpose, such as
cooking, from which smells could penetrate into the wards ;
and, when possible, it is best not to continue the staircase
into the basement.
7. There is ^ limit to the numbers which should be congre-
gated under one roof. This limit will depend very much on
the nature of the cases. A careful consideration of the experi-
ence of military hospitals, into which many slight cases are
received, led to the conclusion that 136 cases should be the
largest number placed in one double pavilion, divided into two
equal halves in such a way as to cut off* by through ventila-
tion the communication between the two halves. In town
hospitals, where the cases are of a more severe character, a
similar double pavilion should probably not contain above
80 to 100 beds.
The passage lobbies and staircases connecting the two
halves of a double pavilion should be well lighted by large
windows, and provided with ample ventilation direct from the
open air; in cold weather they should be supplied with
the Internal Arrangements of Buildings. 1 69
warmth and fresh warm air independently of the wards and
ward offices.
The size of any given hospital ought not to be determined
by increasing the number of beds in any one building, but by
increasing the number of units, each containing the numbers
of beds mentioned ; and the extent to which these units
should be multiplied might, if the units have been properly
constructed and arranged, be determined not so much by
the number of patients as by considerations of economy in
administering the hospital.
In addition to the larger wards, it is necessary to have a few
wards of one or two beds each for special cases ; but these
should be as few as possible, so as to economise labour in
nursing ; and their position must be adapted in each hospital
to suit the arrangements of the principal wards, so as to afford
easy supervision by the nurses.
It is moreover desirable that if convalescent patients remain
in the hospital they should have rooms in which they can
dine and spend the day apart from the other sick ; the situa-
tion of these rooms should be such as not to interfere with
the light and air of the wards. This class of patients also
requires a chapel. It is, however, a subject for consideration
whether, as a rule, patients who are able to move about in
this way should be retained in hospitals.
Arrangements for the several requirements above described
must all be made subservient to the broad general principle of
giving air and light to the wards.
The corridors connecting the units may, in a warm climate,
consist of an open arcade ; in our climate in cold weather a
closed corridor may be necessary : closed corridors should be
lighted by Windows on both sides, capable of opening wide, or
of being removed altogether in warm weather ; the corridors
should be cut off from the adjacent pavilions by swing doors
and be provided with separate means of ventilation, as well as
with an independent supply of fresh warmed air in cold weather.
170 Conditions affecting
These arrangements prevent draughts, and cause the
corridors, lobbies, and staircases to be the means of effectually
cutting off the ventilation of one pavilion from that of another.
The staircases for patients should be broad and easy ; the
rise of each step should not exceed four inches in height, and
the tread should be at least one foot in width ; there should
be a handrail on each side, and a landing after every six or
eight steps.
The considerations which these data suggest are equally
applicable, with modifications suited to the special case, to all
buildings in which large numbers are congregated.
The sanitary condition of dwellings which are built for a
special purpose, such as barracks, workhouses, hospitals, or
asylums, can be easily controlled. There the occupation is
continually of the same description. But in ordinary resi-
dences, the conditions are continually subject to change from
the necessities or caprice of the occupants. In the houses of
the rich, inconveniences arise from rooms built for every-day
life being occasionally used for the reception of large numbers
of people. Thus a dining-room which would be supplied with
adequate fresh air for twelve people is sometimes used to contain
thirty to dine, in addition to servants and numerous lights.
Drawing-rooms adapted for a small number are often filled
so full as barely to afford three square feet of surface per occu-
pant, and are lighted by numerous gaslights or candles.
Rooms intended to be frequently applied to receptions or
dinners, either in private houses, hotels, or municipal build-
ings, should be provided with permanent arrangements for the
renewal of the air on a sufficient scale.
The heat which is generated by persons and lights will
suffice in this country for affording a sufficiently strong
upward current in shafts to ensure the removal of the
necessary quantity of air, provided the shafts are properly
the Internal Arrangements of Buildings. 171
proportioned, and provided adequate inlets for fresh air be
supplied. Dinners and receptions are limited in duration,
hence it may be assumed that 750 cubic feet of air per hour
supplied for each guest, servant, and candle, reckoning a gas-
burner as two candles, would suffice. When arrangenjents for
the removal of vitiated air and the inflow of fresh air have not
been provided in the building, temporary arrangements may
be resorted to, such as have been proposed by M. Joly of
Paris and Mr. Verity in England ; viz. by means of a small
fan worked by hand or by water power, which forces air into
the rooms through a perforated india-rubber or other pipe laid
temporarily along the cornice in a- convenient situation. But
such an arrangement is only a makeshift to remedy defects
in the original construction of the building.
Artificial Lighting.
The impurity of the air caused by artificial light is very
serious. Lamps, candles, and gas-lights, each consume the
oxygen and produce carbonic acid.
An oil-lamp with a moderately good wick burns about i54
grains of oil per hour, consumes the oxygen of about 3*2 cubic
feet of air, and produces a little more than \ a cubic foot of
carbonic acid ; i lb. of oil demands from 140 to 160 cubic
feet of air for complete combustion.
A tallow candle of 6 to the lb., burns about 170 grains per
hour, consuming the oxygen of about 4 cubic feet of air;
I lb. of tallow requires about 170 feet of air for combustion.
Coal-gas consists of olefiant gas and analogous hydro-
carbons and hydrocarbon vapours, all of which contribute to
its illuminating properties. It also contains hydrogen and
marsh-gas, and in addition carbonic oxide, carbonic anhydride,
sulphuretted hydrogen and other sulphur compounds ; these
latter are impurities.
The following table (from Dr. Tidy's Handbook of Chemis-
172
Conditions affecting
try) shows the composition of gas from cannel and from
common coal.
Illuminating power com-
pared to sperm candle
burning 120 grains per
hour, the ^as burning
5 cubic feet.
Composition in xoo volumes.
X
c
X
25-82
47.60
u
1
1
■
.1
1
Heavy Hydrocar-
bons, (C„H2)«.
Equal to Olefiant
gas, CaH*.
Nitrogen, Oxygen,
and Carbonic Acid.
Cannel gas .
Coal gas
34-4
13*0
51-20
4^-53
7-85
7.83
1306
3-05
(32.08)
(6-97)
3.07
• • •
I cubic foot of coal-gas will (according to the quality of the
gas) unite with from -9 to \*6\ cubic feet of oxygen, and pro-
duces on an average 3 cubic feet of carbonic acid, and from -2
to '5 grains of sulphurous acid. In other words, i* cubic foot of
gas will destroy the entire oxygen of about 8 cubic feet of air.
The presence of i per cent, of carbonic acid in gas is said
to decrease the light 6 per cent. To obtain a maximum light
from any flame, the supply of air must not be excessive,
otherwise the carbon particles are consumed before they are
sufficiently heated to emit light, and the excess of atmospheric
nitrogen serves to cool the flame and decrease its illuminating
power. If, on the other hand, the supply of air is too limited,
the carbon passes off unburnt, and the flame becomes smoky.
When gas is only partly burnt in a room, nitrogen, water,
carbonic acid, carbonic oxide, sulphurous acid and other im-
purities, may escape into and vitiate the air.
It is most important to the purity of the air of a room that
the products of the combustion of gas should not mingle with
the air. Several forms of lights have been designed for this
purpose, but as a rule they do not entirely fulfil their object,
for in many cases they conflict with the other arrangements
for ventilation. Thus, if a sunlight is placed in the ceiling, its
proper action is to carry off" a large volume of air from near the
the Internal Arrangements of Buildings. 173
ceiling ; an open fireplace in the room draws a large volume
of air towards itself. The currents conHict, and the fumes
from the sun-burner are liable to be drawn into the room.
In the case of a gas globe lamp suspended in the middle of
the room, supplied with fresh air from the room, with a pipe to
carry oflf the fumes leading from the light up to the ceiling,
and along the ceiling into the chimney, the smallness of the
Fig. 34. Ventilated Gaslight.
pipe, the bend, and the horizontal length, all contribute a large
amount of friction to diminish the draught in the tube : in
rooms where there is no arrangement for replacing the air
removed by an open fire, cross currents will sometimes prevail
in the chimney-flue, especially if it is large. Whenever the
draught in the tube is slu^ish, the Are in the chimney draws
down some of the fumes directly towards the fire; conse-
quently it is very rare that, even with this class of burner, the
fumes of the gas are removed.
The only safe plan is to place the gas-burners in a globe
entirely cut off from the room, supplied with fresh air directly
1 74 ' Conditions affecting
from the open air, the fumes being also carried directly into
the open air. Such an arrangement is very simple in the case
of an outside wall, and this is the only system which will keep
the air of a room free from the fumes of gas. By the arrange-
ment in Fig. 34 the fresh air is supplied through the grating
C, passing along the outer tube to the globe,. and the heated
fumes pass up and away through the inner tube. When wind
blows on the opening the pressure is equal on both tubes, and
if the joints in the room are all air-tight the flame is not
affected by wind.
The electric light, if it be ever perfected for domestic use,
may, it is to be hoped, relieve us from some of the sanitary
defects experienced with other forms of lighting; but the
electric light disengages nitric acid, and it will therefore require
to be kept in a receptacle cut off from the air of the room.
. Workshops.
In workshops the purity of air should be maintained by an
adequate removal of vitiated air, and a supply of fresh air at
the temperature which may be either necessary for comfort or
required in the processes carried on in the workshop. With
adequate renewal of air a temperature of from 75° to 78"* or
higher can be easily .borne, whereas without such renewal of
air lower temperatures soon become oppressive. In work-
shops where the processes carried on occasion fumes, steam,
or a large amount of dust, special extraction should be
arranged by means of rapid currents of air to carry off the
steam, fumes, or dust as soon as it is created, so as to prevent
its mixing with the air of the room.
Stables.
It has not yet been ascertained how much fresh air
is required to keep a horse in health. Such an inquiry,
although of great value when warmth has to be combined
with ventilation, is of little comparative importance as applied
the Internul Arrangements of Buildings. 175
to stables, because the horse is not an exotic animal requiring
artificial warmth. He is taken from a perfectly open-air life,
with its vicissitudes of weather and temperature, to be confined,
more or less, in a stable for purposes quite apart from his
health. The question is, how to subject the horse to the
captivity he has to undergo in serving man, without injuring
him ih his health a;nd strength.
Animal life is most perfectly developed, and its functions
are most perfectly performed, under the conditions of free
diffusion of the atmosphere, including absence of stagnation,
abundance of light, good drainage, absence of nuisance, and
sufficient space to live in.
These are the conditions (besides of course food and drink)
which nature requires for the horse.
Good stable ventilation includes the other conditions, because
if the stable is filthy or ill-drained, or the ground saturated
with putrid urine, it must be obvious that no amount of fresh
air passing through the stable will keep it sweet and whole-
some. Any amount of fresh air coming in will immediately be
tainted by filth which has already collected there.
Again, if a stable be ever so clean or well drained, it will
never be well ventilated without perfect freedom of movement
of air through every part of it, together with free ingress and
egress of air, so provided as to prevent hurtful blasts falling on
the horses.
A fundamental requirement in all stables is paving of such
a character as to wear well, not to become slippery, to be
water-tight, and to be easily cleansed.
Another fundamental requirement is good stable drainage.
Surface drainage is the only kind of drainage applicable
to the interior of stables.
The drains, like the stable floors, should be impervious to
moisture. They should always be made of smooth material,
with as few joints as possible, be carefully laid, having a shallow
saucer-shaped section, and with as rapid an incline as it is
176
Conditions affecting
YatttUbmr to UuSi
airbnelu
h-ieh »X»
Section of a Loose Box 1 7ft. x i aft.
VwwMt
^ Om/iWMf . "I
CeuTMOfatrMeM
mtfcj* tanw
vrj»«/a*>li«dt
" '- car»«
rb-UkijA
Section of Stable.
Elevation of Stable.
Windxrw^ orer trejy Stall ia-s? jtAv-zjiUt jetween f-^rj two atalls
^heJlcm SK^fatB jbn^jy
Fig. 35. plan of Stable.
the Internal Arrangements of Buildings. 177
possible to obtain. They should pass behind the line of stalls,
and be conducted in as straight a line and by as short a course
as possible to the outside of the stable, where they should be
discharged into an underground drain, over a trapped gulley-
grating, placed at a distance of some feet from the stable wall,
so as to prevent effluvia returning, and to prevent dung and
straw from entering the drain.
The mast scrupulous cleanliness of the surface of the stable
should be enforced.
The great principle which ought to be kept in view in
stables is to have the air moving freely through every part of
them, above and around the horses when they are standing,
and in all the angles between the floor and walls when the
horses are lying down, and every horse should have sufficient
ventilation for himself without being obliged to breathe the
foul air of his neighbours. These conditions would be most
completely obtained in an open shed, such as is used for
stabling horses in warm climates, and the nearer we can
approach to this construction, keeping in view the necessity
for protecting horses in this climate, while at rest, from
extreme cold and cold blasts of wind, the healthier will be the
stable.
That form of construction which affords the maximum of
facility for obtaining a free moving atmosphere throughout the
body of the stable is the open roof with ridge ventilation
carried all the way along.
Where the roof of the stable is not open, but flat and
impervious, the distance between the effective ventilating
openings, whether windows or other apertures, corresponds
of course to the breadth of the stable. But with an open roof
and ridge ventilation the distance is reduced to one-half, while
the difference of height above the ground between the ridge
opening and the side windows ensures a far more certain and
continuous movement of the air than could by possib*ility take
plaee with side windows, unless a high wind were blowing.
N
178 Conditions affecting
Therefore a stable with ridge ventilation is the most healthy
stable.
A flat impervious roof, a hay-loft, or a barrack-room over
a stable increases the difficulties of ventilation.
In so far then as concerns the general movement and
renewal of the mass of air in a stable, the form of construction
which effects this most easily and efficiently is an open-roofed
stable, with ventilation along the ridge, swing windows along
the sides, and a continuous inlet for fresh air under the eaves
made of perforated brick, so arranged as to throw the entering
currents up towards the roof
A great incidental advantage of the open roof should not
be overlooked, and that is the facility with which it enables
the stable to be thoroughly well lighted. Light is in its place
as essential to health as air, and moreover, when introduced
vertically from the roof, it enables the state of cleanliness of
the stable to be seen at once.
Besides providing for free movement of the mass of air
within the stable, it is necessary in all stables, but in some
much more than in others, to supply fresh air near the ground-
level at the head of each stall, so that the horse may have
fresh air to breathe when he is lying down.
The reason of this necessity is that in all stables the stratum
of air next the floor-level is the most impure, and will always
be the most impure under any improved conditions of drain-
age and paving. Besides this, the horse, in lying down, places
his head close to the angle between the floor and the wall
where the air is stagnant.
It follows from what has been said that the easiest and
most efficiently ventilated stable is the open roof partially
glazed, with ridge ventilation all along, ventilation at the
eaves, a swing window for every stall, and the horses* heads
turned outwards, with a proper air-brick in the outer wall,
introduced 6 inches from the ground between every two stalls.
With these conditions of ventilation the Barrack and
the Internal Arrangements of Buildings. 1 79
Hospital Improvement Commission stated that each cavalry
horse should have 1600 cubic feet and 100 superficial feet of
space.
General Morin states that the cubic space allowed in French
cavalry stables is 1750 cubic feet per horse, and he lays it
down that 7000 cubic feet is the volume of fresh air which
should be supplied, or of vitiated air which should be removed,
per horse per hour.
N2
CHAPTER XIV.
CONDITIONS AFFECTING MATERIALS AND DETAILS
OF CONSTRUCTION.
In every dwelling dryness is an essential of health. In
this climate it is necessary to provide for warmth. In a
hot climate coolness is sought. In a hot climate, or for hot
weather, the roofs and walls should be of such construction
as to prevent the temperature inside a house being raised
by the heat of the sun. For cold weather, on the other hand,
the roof and walls must keep in the heat, so as to main-
tain the air of the house at a higher temperature than the
outside air.
The materials and constructional arrangements best
adapted to keep warmth in a house will to a considerable
extent be effective for keeping out the heat.
The temperature which can be maintained in a house
will greatly depend on the construction of the walls, and
on the materials of which they are composed. Materials
differ greatly in their power of allowing heat to pass through
them.
The following examples, showing for different materials
the units of heat transmitted per square foot per hour by a
plate I inch thick, the two surfaces differing in temperature
1° Fahrenheit, illustrate their relative advantages in this
respect.
Conditions affecting Materials^ &c. i8r
Marble, grey fine-grained , .
Do. white, coarse-grained
Stone — ordinary freestone
Glass
. . 28
• . 22
. . 13-68
. . 6.6
Brickwork .......
. . 483
Plaster 3.86
Brickdnst i'33
Chalk powdered •Sy
Fir planks .•..,.... i<37
Increased conductivity of heat in a material must be
counteracted by increased thickness. All ordinary wall
materials admit of a greater or less change of air through the
material itself, depending upon the extent to which the
material is porous.
The porosity of a material is shown by its power to absorb
water. The following ^ is the percentage of its own weight of
water which each of the materials mentioned below has been
found to absorb —
Bricles,
percent.
Malm Cutters 22
Malm Bright Stock .... 22
Malm Seconds 20
Brown Paviors 17
Hard Paviors 9J
Common Grey Stock ... 10 J
Hard Do 7}
Washed Hard Stocks ... 4 J
Staffordshire—
Common Blue 6*5
Dressed Do 2.3
Brown glazed brick .... 8*6
Stones.
Good Granite
Indifferent Do. .....
Bad specimen Do
Trap and Basalt ....
Sandstone —
Craigleith
Parkspring
Mansfield
Hassock (very bad quality)
Limestone —
Marble
Portland
Ancaster
Bath
Chilmark
Kent Rag
Ransome Artificial stone . .
percent.
• 1
I
. 3
a trace
8
8
10-4
20
a trace
13-5
16.6
8.6
H
12
From this it appears that brick and stone walls, being
always more or less porous, must admit, as already mentioned,
of a considerable spontaneous change of air when dry.
' See Notes on Building Construction, Science and Art Department, 1879.
£82 Conditions affecting Materials
Porous walls tend to absorb the moisture given out in
breathing, or in the combustion of lights. In this process
walls absorb organic and other impurities, which after a time
decay, and the wall may become a source of impurity for the
air. When a wall is damp, change of air can no longer go on
through it. The evaporation from the wall cools down the
temperature. Damp in walls is considered to be a cause of
fever, especially in warm climates. The damp wall, whilst it
checks the passage of the air, is cold, and consequently
occasions a rapid radiation of heat from persons sitting within
its influence. On the other hand, in hot and dry climates,
wet mats are often hung over all openings, as a means of
cooling the air without injury to health. These represent
absolutely pervious walls, admitting of a rapid change of air.
In this climate, damp walls, besides being unhealthy, are
uneconomical. They cause a great absorption of heat by the
evaporation of the moisture from the surface. New walls are
always damp. The quantity of water which will be contained
in a new wall is very remarkable. Suppose that 100,000
bricks are used for a building, each weighing seven pounds ; a
good brick can suck up from 10 to i^o per cent, of its weight
in water, but assume 7 per cent, as what gets into it by the
manipulations of the bricklayer. Also assume that the same
amount of water is contained in the mortar, a quantity
certainly much understated ; the mortar forms about one-fifth .
of the walls ; thus nearly 100,000 pounds of water, equal to
10,000 gallons, may be assumed to be put in the walls in the
process of building, and which must be removed from the
walls of the house before it becomes habitable. This water
must be removed by evaporation into and by the air. The
capacity of the air for receiving water depends on the different
tension of the vapour at different temperatures, on the quantity
of water already contained in the air as it flows over this
moist surface, and finally on the velocity of that air. Assume
the average temperature of the year to be about 50° Fahren-
and Details of Construction. 183
heit, and the average hygrometric condition of the air to be
75 per cent, of its full saturation. At the temperature named
one cubic foot of air can take up four grains of water in the
shape of vapour, but as it contains already 75 per cent, of these
four grains, which amounts to three grains, it can only take up
one additional grain. As often then as one grain is contained
in the 10,000 gallons of water mentioned above, as many
cubic feet of air must come in contact with the new walls, and
become saturated v/ith the water contained in them ; or, about
700,000,000 cubic feet of air are required to dry the building
in question. I'herefore the drying of a building will be best
effected by passing a large volume of air through it, and air
at a higher temperature, and therefore of a greater hygro-
metric capacity than the outer air, will effect this object mfT^t
rapidly.
Until this damp has been expelled by fires or by time, the
building should not be occupied ; when the walls have been
dried inside, it is the proper function of the walls to prevent
damp from entering from the outside. Damp should be
precluded from rising into the wall from the ground by means
of a damp course carried round in all the walls below the
level of the lowest floor. The damp course may be of slate,
asphalte, or glazed perforated bricks, this latter form of damp
course has the advantage of allowing air to penetrate on all
sides uniformly under the basement floor.
Damp should be prevented from descending into the wall
from above by an impervious coping or by eaves. Improperly
laid copings will act as conductors of wet into the wall, rather
than as protectors against it. Projecting eaves are advan-
tageous; the more they project, the greater protection do
they afford to the surface of the walls. The rain which beats
against a wall will be partly evaporated out again by the
action of the air and sun, and partly drawn through it by
capillary attraction ; and if the material is very porous, or the
wall very thin, it may saturate the wall. The capillary action
184 Conditions affecting Materials
will be checked by joints in brick or stone work, and arrested
by air-spaces in the wall or by the use of a hollow wall.
The heat generated in rooms passes away in cold weather
through the floor, ceiling, and walls and windows into the
open air or adjacent colder parts of the house, and the heat
of the house is similarly constantly passing away into the
open air through the walls and the windows and the roof.
The temperature of the basement floor when below the
level of the adjacent surface will be practically that of the
mean annual temperature, and will therefore occasion little
loss of heat.
The loss of heat by walls varies in a direct ratio with the
conducting power of the material of the walls, and with the
diff"erence of temperature between the inner and the outer
surface of the wall, and it varies inversely with the thickness
of the wall. The actual temperature of the surface of the wall
is troublesome to ascertain ; if instead of the temperature of
the surface of the wall, the temperature of the air inside the
building and outside be taken into account, the formula be-
comes somewhat more complicated, and varies in a direct ratio
with the conducting and radiant power of the material of the
wall, the loss from contact with air, the difference of tempera-
ture between the air inside and that outside, and in an inverse
ratio with the thickness of the wall.^
* If T" «s temperature of internal air,
7"«= temperature of external air,
R a radiant power of the material,
A s loss by contact of air,
C — conducting power of the material,
27 8s units of heat per hour,
E « thickness of the wall in inches,
the rule is —
^_ (AxC)((l)x(T-r)
{Cx[2XA + R]}+ {ExAxQ^}'
From Box on Heat.
and Details of Construction. 185
The loss of heat by a vertical wall from contact of cold air
per square foot of area will be greater with a low wall than
with a high wall. The reason is obvious; the cold air in
immediate contact with the lower part of the warmer wall
receives heat from it, and ascends, and at each successive
gradation in height the difference of temperature between the
air and the wall is decreased by these successive increments
of heat, and the amount of heat given out by the wall to the
air is thus progressively diminished as the air reaches the
upper part of the wall, in a proportion dependent on the
square root of the height.
Thus whilst a vertical plane i foot high would lose -5945
units of heat per square foot per hour for each 1° Fahrenheit
difference in the temperature between the surface of the plane
and the adjacent air, a vertical plane 10 feet high would lose
•4350 units of heat per square foot, one 40 feet high would
lose "3980, and one 100 feet high would lose '3843 units per
square foot.
The problem connected with the loss of heat by walls
requires more space for its full discussion than a treatise of
the nature of this one, limited to the general enunciation of
principles, will admit of. For the special study of the
question P^clet, Balfour Stewart, Box on Heat, and other
writers may be advantageously consulted. From the latter
work, which is eminently practical in its character, the follow-
ing table is extracted. The units of heat transmitted per
square foot per hour by a plate i inch thick, the two surfaces
differing in temperature 1° Fahrenheit, being as shown by
P^clet's experiments previously alluded to —
for ordinary stone = 13*68,
for brick-work = 4*83.
The table shows the loss of heat per square foot per hour by
brick and stone walls, 40 feet high, in buildings where only
one face is exposed, and for 1° difference of internal and
external temperature.
1 86
Conditions affecting Materials
Brickwork.
Stone.
Thickness.
Units of Heat.
Thickness,
inches.
Units of Heat. !
brick, inches.
i= 4i
•371
6
•453
I = 9
•275
12
•379
ij« 14
•213
18
•324
2 » 18
.183
24
.284
3 = 27
.136
30
•257
4 =36
.108
36
'2 28
The number of units of heat lost through a hollow wall, or
wall with an air-space in the centre, is less than that through a
solid wall. The units of heat, dissipated by the outer air, will
be in a direct ratio to the difference between the temperature
of the air-space in the wall and that of the outer air ; whilst
the effect of diminished thickness in the wall follows an
inverse ratio somewhat less than that of the actual diminution
of thickness of the wall. For instance, if the difference of
temperature between the room and the outer air = t^ and the
temperature of the air-space be a mean between that of the
room and the outer air, then the difference of temperature
between the air-space and the outer air will equal \ /, and if
further the thickness of the wall be jE", and the air-space be in
the middle of the wall, so that the thickness on each side of
the air-space = i -£", the formula in the preceding note for
ascertaining the value of the units of heat lost in each case,
expressed briefly would assume the general form, in the case
of the wall without an air-space, of -^ — ^rvv and in the case
of the wall with an air-space, of — ,^ y^ ^r ' or, if we assume
from the previous table a wall of a room 9 inches thick,
with a temperature in the room a° above that outside, the
loss of heat would be -550 units per square foot per hour. If,
on the other hand, two walls half a brick (or 4^ inches) thick
and Details of Construction. 187
each, were used on each side of an air-space instead, and the
temperature of the intermediate air-space was 1° above the
outer air, and 1° below the temperature of the air of the
rooms, the loss of heat would be '371 per square foot per
hour, or about two-thirds of the heat lost by the solid wall.
The loss of heat, as well as the porosity of a wall, is in-
fluenced by wall coverings, such as stucco outside ; or plaster,
cement, or papering inside.
Independently of the advantages which may be derived from
the smaller conductivity, if any, of the covering material, each
layer forms an additional break in the continuity of any one
material, and lessens both the porosity and the loss of heat.
The best internal wall-surface for a dwelling would be an
impervious polished surface, which would not absorb moisture
from breathing, and which, on being washed with soap arid
water, and dried, would be made quite clean. This wall would
not absorb organic matter, but when colder than the air of the
room, the moisture from the breath, &c., would be condensed
upon the wall. To prevent this, either the temperature of the
wall should exceed that of the air, or a larger volume of air
would require to be passed through a room with impervious
walls than a room with pervious walls. In conveying warmth
to rooms with impervious walls by an agency different from an
open fire, it would be preferable to convey it in such a manner
as to warm the walls, and warm the air of the room through
their means. An enamelled metallic wall surface, with a space
between the surface and the brick or stone wall for the
passage of warmed air, would effect this object.
Plaster, wood, paint, and varnish, all absorb 'the organic
impurities given off by the body, and any plastered or papered
room, after long occupation, acquires a peculiar smell.
In a discussion, in 1862, in the French Academy of Medicine,
a case was mentioned in which an analysis had been made of
the plaster of a hospital wall, and 46 per cent, of organic
matter was found in the plaster. No doubt the expensive
1 88 Conditions affecting Materials
process which is sometimes termed enamelling the walls,
which consists of painting and varnishing with repeated coats,
somewhat in the manner adopted for painting the panels of
carriages, would probably prove impervious for some time, but
it would be expensive, and very liable to be scratched and
damaged.
Parian cement polished is practically an impervious material,
but It is costly; unless carefully applied, its appearance is
unsatisfactory, and it can only be applied on brick or stone
walls, and not on wood-work or partitions, because, being
inelastic, it is liable to crack. The want of elasticity in Parian
cement is unfavourable to its use in ceilings.
The numerous joints required for glazed bricks, or tiles,
render the use of these questionable as wall linings. The
cement of the joint being more or less porous is sooner or later
discoloured. Moreover, cracks and joints are objectionable, as
they get filled with impurities, and may even harbour insects.
In default of any impervious covering, the safest arrange-
ment in hospital wards is plaster lime-whited or painted,
which should be periodically scraped so as to remove the
tainted surface, and be then again lime-whited or painted. In
hospitals, of course these arrangements require the wards to
be periodically vacated ; but this is of itself an advantage, be-
cause every ward should be left empty annually for a period.
When plaster is used, it is essential, for the reasons before
mentioned, that at the expiration of a number of years,
dependent upon the degree to which the room has been
occupied, the whole outer coat of plaster should be removed
from the walls and ceilings, and new plaster substituted.
When walls are re-papered, the old paper should be invariably
removed, as it is saturated with organic matter. In all places
occupied by many persons, such as hospital wards, barracks, or
asylums, the walls and ceilings should be quite plain, and free
from all projections, angles, or ornaments which could catch or
accumulate dust.
and Details of Construction. 189
In connection with wall coverings, it is necessary to allude
to the danger of poison in wall-paper or paint. Arsenic is the
substance from which this danger is generally found to arise.
Green paper, as a rule, contains more arsenic than others ;
but colour in paper is no guarantee of freedom from arsenic.
If not in the colour itself, it may still be in the mordant dyes
or other material used in the manufacture of the paper.
Arsenic in various combinations more or less dangerous is
used in a great variety of colours. Many French greys and
neutral tints, and some white papers, are as heavily loaded as
green. Nothing but an examination of the individual sample
of paper or colour will afford security against its presence.
The danger is in proportion to the quantity of arsenic or
mineral poison used in the colouring matter of the paper ; and
in proportion to the facility with which it may be removed
from the fabric, either as dust or gas.
Danger from arsenic as a colouring matter seems to depend
in part upon the presence of size. Dr. Fleck showed by
experiment that a mixture of arsenious acid and starch paste
or other organic substance gives rise to the formation of
arseniuretted hydrogen, but no arsenic could be detected in
air which had been in contact with a mixture of arsenious
acid and water without the presence of organic matter.
Arsenic is frequently present in distemper, which being
mixed with size forms a direct combination of arsenic and
organic matter, liable to give off arsenic under many circum-
stances ; and in the case of damp walls it is there ready for
the development of arseniuretted hydrogen.
Arsenic is a powerful antiseptic, and hence the danger of its
being introduced into glue and size, because it is so effectual in
preventing decomposition, and is free from smell ; moreover,
size is largely used for fixing colours. In purchasing wall-
papers a guarantee should be required from the seller ; but it
is also desirable to have the specimen analysed.
190 Conditions affecting Materials
Floors,
One of the most important conditions to be observed in the
materials for floors in this climate is that they should not
be cold to the feet, consequently wood floors are desirable,
unless the tiled floor is arranged so as to be warmed on the old
Roman plan — v\z, by means of tiles laid with a hollow space
or flues underneath, warmed by the smoke or heated gases
from a furnace.
Concrete, cement, and stone and brick more or less permit
the passage of damp ; therefore the floor, of whatever material
it be, should always have an air-space under it so as to ensure
dryness.
The basement floor of a house may have an important
influence on the purity of air. The heat of the basement floor
will be substantially that of the ground under it, and that
temperature differs but little from the mean annual tem-
perature of the ground. The basement will thus be cooler in
summer and warmer in winter than the outside air. This
warmth tends to cause the air to rise through the house, and
hence in cold weather, if warmed fresh air is not otherwise
provided in a house, and if there is a basement, the air will
be liable to pass up from the basement and pervade the
house. Consequently, in such a case, the purity of the air in
the house will depend upon the purity of air in the basement.
The purity of air in the basement will depend upon the
arrangements for keeping all refuse and objectionable things
out of the basement itself, but it depends especially upon the
ground-air in the subsoil under and around the house being
entirely cut off from the basement. To secure this, a con-
tinuous bed of concrete, or a layer of asphalte should be laid
over the whole surface covered by the house, and sufficient
areas should be carried below the level of the basement so
a§ to cut the ground-air off* by an open airspace from the
adjacent soil.
and Details of Construction, 191
In order further to diminish the liability of ground-air to
penetrate into the basement, there should be an air-space
between the ground and the floor of the basement.
The floor of the basement, whether it be of wood, of stone,
or of tile, should be from one foot to eighteen inches above the
level of the surface of the ground around and under it : joists
supporting the floor should not be laid on the ground, but
should have a space underneath, to which a free circulation of
air should be admitted, by means of gratings communicating
with the outer air.
Drains should not be carried under the basement-floor.
The only case in which it is advisable to dispense with an
air-space under the floor would be when the floor is of tiles or
of wooden blocks embedded in asphalte, to ensure dryness.
A floor of wooden blocks laid on and bedded in asphalte
combines dryness with warmth for the feet.
With wooden huts care should be taken to level the ground
under the floor, and to allow of free circulation of air, either
between each pair of joists, or, what is preferable, to raise the
joists so as to allow free circulation under the whole floor.
Floors should be laid with close joints, and wooden floors
should be tongued, so as to prevent dirt from falling through and
accumulating under the floor, as such dirt is liable to putrefy.
The frequent saturation of wooden floors with water to keep
them clean diff"uses damp ; consequently a closely laid polished
floor of hard wood possesses great sanitary advantages.
For hospitals the floor requires special considerations.
Ward-floors should be as non-absorbent as possible, and for
the sake of warmth to the feet they must in this country be of
wood ; oak, or other close hard wood, with close joints, oiled
and beeswaxed, and rubbed to a polish, makes a very good
floor, and absorbs very little moisture. It is impossible to pay
too much attention to the joints ; they should be like those of
the best parqueterie, aff'ording no inlet for dirt to lodge ; because
the impurities which become lodged in the cracks of a hospital
192 Conditions affecting Materials
floor are eminently objectionable. There should be no saw-
dust, or other organic matter subject to decay, under the
floor. When one ward is placed above another, it is essential
that the floor should be non-conducting of sound, and that it
should be so formed as to prevent emanations from patients
in the lower ward from passing into the upper wards. The
floors of the Herbert Hospital are formed of concrete, sup-
ported by iron joists, over which the oak boards are laid.
An economical and non-absorbent surface for the floor can
be obtained by first laying rough deal boards and covering
them with thin, closely-laid oak boards oiled and beeswaxed.
These oak floors must be treated like the French parquet, by
occasional frottage. A very good hospital floor is that used
at Berlin, which is oiled, lacquered, and polished, so as to
resemble French polish. It is damp-rubbed and dry-rubbed
every morning, which removes the dust. This wet and dry
rubbing process of cleaning is far less laborious than either
frottage or scrubbing, and completely removes the dust and
freshens the ward in the morning. The only objection to this
surface is its want of durability, and consequent necessity for
periodical renewal. Both of the processes above mentioned
render the floor non-absorbent, and both processes do away
with the necessity of frequent scouring, which is objectionable
from the quantity of damp it introduces into the ward. The
French floor stands the most wear and tear, but must be
rubbed periodically by a frotteur, which cleaning is more
laborious than scrubbing. The daily cleaning of a bees-
waxed floor and the removal of dust may be effected by
wiping with a damp cloth wetted with warm water, and
carefully rubbing with a dry cloth. Practically, with care,
a well-laid oak floor, with a good beeswaxed surface, can
always be kept clean and polished in this manner assisted
by periodical frottage.
and Details of Construction. 193
Roofs.
The outer covering of a house should be impervious to
moisture from without; but experience shews that it is un-
healthy to live under a ceiling impervious to air. Air heated
by contact with the human body carries up emanations which,
when they rest upon a pervious ceiling, are retained there,
whilst the moisture passes off through the ceiling; on the
other hand, if these emanations come in contact with an
impervious ceiling, they are not absorbed, and may be again
brought into circulation in the air of the room. Consequently,
if circumstances render it necessary to have a ceiling imper-
vious to air and moisture, this must be discounted by pro-
viding under such impervious covering additional facilities for
change of air in the upper part of the room.
The ordinary lath and plaster ceiling, although a good non-
conductor of heat, allows of a considerable passage of air and
moisture. With a pressure obtained by a difference of tem-
perature of 72° inside and 40° outside, the quantity of air
which was found to pass through ordinary plaster was about
1*5 cubic feet per square foot of area per hour.
The nature of the roof must depend on the materials avail-
able. Thus cement, clay, tiles, wooden shingles, slate, iron,
copper, lead, are used according to circumstances. If good
conductors of heat are used to keep out wet, such as copper,
iron, or slates, some non-conducting material is required
underneath ; for instance, in the case of a slated roof, the
slates should be laid on close boards covered with felt, to
ensure the best protection against heat or cold.
The loss of heat through the roof will depend upon whether
the rooms are ceiled, and upon the form and nature of the roof-
covering. If there is a lath and plaster ceiling to the upper
rooms, and an air-space between the ceiling and the roof,
closed from the outer air, so as to prevent any rapid circula-
tion of air, and if the roof be formed in the most approved
O
194 Conditions affecting Materials
manner in this country, viz. with close boards covered with
felt under the slates or tiles, the loss of heat in winter, and the
effect of heat in summer in raising the inner temperature, will
be comparatively small.
If there is no ceiling, and if the roof be not carefully con-
structed, as above mentioned, the loss of heat will be very
considerable. The loss of heat from glazed roofs, ceilings, and
skylights, and from metal roofs, such as are used in railway
stations and markets, is very considerable.
The air in contact with metal or thin glass exposed to cool-
ing influences is under the most favourable condition for being
cooled. Each layer as it is cooled falls down and is replaced
by warm air, which undergoes the same process. This renders
a space covered with a metal or glass roof without inter-
mediate ceiling very difficult to warm. Therefore in halls or
rooms lighted by a glass roof, or staircases lighted by sky-
lights, it is essential for preserving the heat that there should
be a second glass ceiling below the one exposed to the outer
air ; and in cold weather it may be advisable to adopt special
means to warm the intermediate space, if an equable tempera-
ture is sought to be maintained in the room at all times.
Where glazed ceilings are lighted by gas-lights above the
lower ceiling of glass, the heat from the gas when lighted is
sufficient to keep up the temperature.
In very hot weather, when it is desired to cool down the
temperature of an iron or glass roof, it may be watered by
jets from 8 or 9 o'clock in the morning till about 5 o'clock
in the evening. The quantity of water would however be
considerable, probably not less than about 25 gallons per hour
per square of 100 feet. The practice of lime-whiting the roof,
which is largely resorted to in some places, is a great protec-
tion against heat.
Windows should be carried up as near the ceiling as possi-
ble. In a low room this is essential, in order to freshen the
air. In a lofty room it is equally necessary, in order to pre-
and Details of Construction. 195
vent the warm impure air which has risen to the top from
cooling, falling, and remixing with the air in the lower part of
the room.
Therefore if the tops of the windows are much below the
ceiling there should be openings above the windows f6r change
of air. Moreover, whilst it is an element of cheerfulness in
a room for the upper part of the windows to be near the ceil-
ing, it is equally important that the sills of the windows should
be brought down near to the floor.
Similarly, it is an element of cheerfulness to splay the sides
of window openings.
The proportion of window surface to the cubic contents of
the room must to some extent depend on the climate and
aspect.
In England, adequate light will generally not be obtained
with less than one square foot of window-surface to about 100
cubic feet of the contents of the room. In hospital wards, one
square foot to 60 cubic feet of content is desirable. This
should be a minimum allowance, and assumes that the win-
dows in all cases are of clear glass ; but greater cheerfulness
will be secured by more light. In climates with bright sun-
shine less light may be found sufficient. Where light is abun-
dant it can always be modified, when desirable, by sunshades
or blinds ; but if window openings are small, light cannot be
increased at will.
The amount of light afforded by a window is considerably
modified by the quality of glass.
In some recent experiments :—
Polished British plate glass, \ inch thick, intercepted 13 per cent of the light,
36 oz. sheet glass , 2%
Cast plate glass, \ inch thick, .... „ 30 „
Rolled plate glass, 4 corrugations in an inch „ 53 „
»» *>
- »t
Clear glass is thus of great importance, and the thicker it is,
consistent with clearness, the better, because thin glass allows
of a more rapid loss of heat.
02
196 Conditions affecting Materials
Good glass is desirable, because dust adheres easily to bad
glass, but not to good glass ; and the surface of bad glass is
more or less rapidly rendered uneven by exposure to the
atmosphere, whilst good glass is unaltered by long exposure.
The quality of glass depends upon the admixture of the
ingredients. The percentage composition of window glass
is 66'37 of silica, i4'23 of soda, ii«86 of lime, 8*i6 of alu-
mina; that of plate glass 73-5 of silica, 5-5 of potash, 12 of
soda, 5'5 of lime, y^ of alumina. A soda glass is more
fusible and more brilliant than a potash glass. But soda
imparts a slightly green tinge to glass, which does not occur
with potash. Lime diminishes the fusibility of the glass,
imparts no colour, and increases its hardness and lustre.
The most convenient form of window for ventilation in
ordinary dwelling-rooms in this country is the sash-window,
opening top and bottom. This mode of construction assists
ventilation in the manner already described by enabling a
current to be maintained, fresh air passing in below whilst
the vitiated air of the room passes out at the top. Ventilation
should not however be dependent only on windows. In
hospitals, where the wards, and consequently the windows, are
lofty, the lower part of the windows may be advantageously
constructed of tlie sash form, whilst the upper part is hinged
on a transom so as to open inwards, and thus facilitate the
inflow and outflow of air, on the plan of a hopper ventilator.
In hot climates the French window is advantageous, as it
enables the whole window opening to be utilised for supplying
fresh air.
The loss of heat through windows amounts to that lost by
radiation added to the loss of heat by contact with air.
It may be assumed with thin glass that the temperature of
the outer surface of the glass is a mean between the tempera-
ture inside the room and that of the outer air.
For thin glass, adopting the previous notation in the note,
page 184, U=(,R^A){T--P).
and Details of Construction. 197
With thick glass the conducting power of the material must
also be taken into account, as in the case of a wall.
The loss of heat with double windows is much less than
that with single windows, and they have the advantage not
only of transmitting less heat, but, from the temperature of
the inside glass being greater, less radiant heat is absorbed
from the occupants of the room. P^clet found that the loss of
heat in double windows increased somewhat with the distance
apart of the inner and outer glass, owing probably to the
greater facility for currents of air in the wider space between
the glass.
Thus with an intermediate space between the windows of
•8 of an inch, the loss of heat of the single window to that of
the double window was in the proportion of i : -47 ; with a
distance apart of % inches the proportion was as i : '55 ;
with a distance apart 2-8 inches, which is nearly what exists
in practice, the proportion would probably be as i : -6.
The proportionate loss of heat by walls, as compared with
the loss of heat by windows, varies to some extent with the
conditions of the room, 1. e. the proportionate extent of wall
exposed to the outer air ; but with 14-inch brick walls, and an
assumed internal temperature of 60° in the room and an out-
side temperature of 30°, the proportion of loss of heat from
wall-surface to loss of heat from window-surface may be
approximately taken to be about 1 : 2*5.
CHAPTER XV.
PURITY OF WATER.
After air, water is the first requirement for existence ; and
impure water is as fertile a source of disease as impure air.
AH available water comes from the rainfall ; if rain falls on
an impervious surface, it runs off in surface streams and rivers ;
if it falls on porous formations, it runs off in underground
streams and rivers.
A cubic foot of water weighs looo ounces, or 62-5 lbs. An
imperial gallon weighs 10 lbs. avoirdupois at 69° Fahrenheit.
Fresh water in cooling becomes denser until the temperature
reaches 39° Fahrenheit ; after this it again expands until it
reaches 31*°, when it solidifies into ice. In the act of freezing,
water expands considerably, and with sufficient force to burst
iron pipes. This is so well known a fact that it is quitp
astonishing how builders and architects continue year after
year to leave water-pipes unprotected from frost.
There are few things which water does not dissolve to some
extent. Its solvent powers are generally increased by rise of
temperature, but there are some exceptions to this. Chloride
of sodium (e.g. salt) is dissolved to the same extent whatever
the temperature ; sulphate of lime is less soluble in hot than
in cold water.
Water absorbs gases in variable amounts — it dissolves
ammonia and hydrochloric acid in large quantities; but it
dissolves the gases of the atmosphere, oxygen, nitrogen, and
Purity of Water. 199
carbonic acid only in small quantities, as will be seen from the
following table : —
Quantity of different gases absorbed by i volume of water at 1 5*C
(yfF) and 30 inches Barometric Pressure,
Volume of gas dissolved
by I voL of water.
781.7000
457.8000
43-5643
1.0000
0.0299'
0*0148
Ammonia ....
Hydrochloric acid
Sulphurous acid (SO,)
Carbonic acid (CO,)
Oxygen
Nitrogen ....
Water usually absorbs more gas the lower the temperature
and the greater the pressure : when water is warmed it gives
out the gases ; when it freezes the dissolved gases are usually
liberated. This is a point of importance in the question of
storage of water.
Rain, as it leaves the clouds, is pure, but in its passage
through the air it absorbs certain gases, and carries with it
particles of matter which may be floating in the air.
The gases it absorbs are oxygen, nitrogen, carbonic acid, a
little ammonia, and nitric acid. The particles floating in the
air are for the most part organic.
Rain water collected from a rocky surface sparsely occupied
by population is the purest attainable water supply.
Near large towns other impurities are found in rain water.
But notwithstanding this, such rain water is generally far
purer than river water. The water found in rivers has either
drained into the rivers from land, or, having fallen on porous
strata, is given out from them in springs. For this reason all
water in rivers or streams contains more or less of matters
taken up from the soil. Thus rivers fed from a granite country
will be comparatively pure, though frequently peaty. There
is no evidence that a little peaty discolouration is injurious to
health.
Rain which falls on cultivated land is liable to pollution
200 Purity of Water.
from the manure intended for the crops. When rain falls on
a closely inhabited surface, or passes into a subsoil saturated
with impurities^ it will be contaminated.
The most agreeable waters are generally those containing
nitrates and chlorides ; such waters should be avoided.
Pure water acts rapidly on unprotected iron pipes — cast
iron is less affected than wrought iron — and a coating of
asphalte or pitch will protect the iron, provided the coating
be perfect. If pure rain water is allowed to come in contact
with lead it will dissolve a part of the metal.
The action of water on lead appears to depend on the
quantity of oxygen and carbonic acid. Where there is a
large quantity of oxygen, the lead is rapidly oxydised, and
the oxide of lead is to a certain extent soluble in pure water ;
but if the water contains a sufficient quantity of carbonic acid
to convert the oxide into carbonate of lead, which is only
slightly soluble, the water will be comparatively safe from
dangerous contamination.
A lead top and lead fittings in a pump of a well have been
found to be injurious, from the evaporated water, which is
pure, condensing on the lead, dissolving some of the metal, and
dripping back into the well. Lead cisterns are subject to the
same effect, and therefore, lead cisterns for storing water
should be avoided.
Peaty matter in water forms a coating which protects the
surface of the lead ; water which has been for some time in
contact with unprotected iron pipes, and has been deprived of
its free oxygen, is less liable to action on lead.
But, in point of fact, the conditions under which water acts
on lead are so intricate that it is preferable, where any doubt
exists, to avoid such water for domestic purposes, if possible ;
or if no other supply is available, to use iron or earthenware
pipes for its conveyance, and slate or earthenware cisterns for
storing it.
Hard water never acts on lead ; it forms a protecting surface
Purity of Water. 201
by the deposition mostly of sulphates, and carbonates of lime
and magnesia.
The effect of hardness of water on health is a somewhat
intricate question.
A comparison made on an average of five years between the
death-rates of twelve towns furnished with soft water, as com-
pared with twelve towns furnished with hard water, showed a
marked preponderance in favour of the towns supplied with
hard water as compared with those supplied with soft water,
10 degrees of hardness being the standard. But the sanitary
condition of the several towns in other respects would require
special examination before this evidence could be admitted as
conclusive.
Of the conscripts taken in France, a larger number were
found to be rejected on medical examination from soft water
districts than those taken from hard water districts. On the
other hand, Highlanders are a stalwart race, and the water
they have is mostly soft water.
Hard water is alleged to produce in some individuals
certain diseases, such as stone ; but, on the other hand, in
valleys in mountainous districts, where the water is practically
pure rain water, the inhabitants suffer from goitre.
The economical advantages for domestic use of soft water are
undoubted, arising especially from the saving of soap. Each
degree of hardness destroys 2 J ounces of soap in each 100 gal-
Ions of water ; therefore, soft water is commercially of more value
than hard water, in the proportion of 5 ounces of soap to each
aoo gallons for each degree of hardness. For many manufactur-
ing purposes soft water is preferable. Thus, dyeing requires soft
water, — on the other hand, ale-brewing requires hard water.
Water of 10 degrees of hardness would probably satisfy the
general requirements of a town supply.
The terms * hard ' and * soft * refer to the soap-destroying
power of a water. Soap is an alkaline stearate. The addition
to it of lime and magnesia decompose it, forming a calcic or
202 Purity of Water.
magnesic stearate. Hence the reason why it is difficult to
obtain *a lather' with hard water (i.e. a water containing
lime and magnesian salts), viz. because a certain quantity of
the soap is required to decompose the calcic and magnesian
salts before a lather can be obtained, whilst, conversely, a
lather is at once formed with a soft water, because of the
absence of calcic and magnesic salts.
Two kinds of hardness are usually described —
Temporary hardness is due to calcic or magnesic carbon-
ates. These salts are almost insoluble in pure water, but
are freely soluble in water containing carbonic acid. On
boiling, the carbonic acid is expelled, and the carbonates are
precipitated. Hence temporary hardness is that hardness
which may be got rid of by boiling the water.
Permanent hardness is chiefly due to the presence of calcic
and magnesic sulphates, and is not got rid of by boiling.
In expressing the hardness of a water in degrees, it is to be
understood that every degree, theoretically, represents one
grain of calcic carbonate, or its equivalent in soap-destroying
power, in one gallon of water.
Hence, the universally-employed test for hardness is the
soap test, originally suggested by Dr. Clarke. This test
consists in employing a solution of soap of known strength,
and ascertaining how much of this solution is required to form
a lather which will last a certain time.
For the purpose of this test, in the first place, i6 grains
of neutral chloride of calcium (prepared by solution of car-
bonate of lime in hydrochloric acid, and repeated evaporation
to dryness, until all the excess of acid is driven off") are
dissolved in a gallon of distilled water, which is then said to
be of 16 degrees of hardness, a solution of soap of a given
degree of strength is then formed. The former of these liquids
is used to graduate the latter. The degree of hardness of the
water to be tested is estimated from the number of measures
of soap solution required to form a permanent lather.
Purity of Water. 203
Chalk waters are notoriously hard waters. They are partially
softened by boiling, and deposit a large amount of fur.
In selecting a water for use it is necessary to determine —
I. The initial hardness.
a. The permanent or irremoveable hardness.
3. The removeable or temporary hardness.
Chalk water may be softened to a considerable extent by
another process invented by Dr. Clarke.
To explain this process it is necessary to consider the com-
position of chalk.
A pound of chalk consists of — lime 9 oz., carbonic acid
(CO2) 7 oz.
The 9 oz. of lime may be obtained separately from CO2 by
burning, e.g. driving off the 7 oz. of carbonic acid by heat.
When so separated the 9 oz. of lime may be dissolved in not
less than 40 gallons of water, and what is called lime-water
obtained.
The 16 oz. of chalk would probably require 5000 gallons of
water to dissolve them — so sparingly soluble is chalk.
But if 7 oz. more of carbonic acid, in addition to the 7 oz.
of carbonic acid in the chalk, be added to the 16 oz. of
chalk in water, then it becomes readily soluble, and bicar-
bonate of lime is formed. If the proportion of such a solution
were 16 oz. of chalk and 7 oz. of carbonic acid to 400 gallons
of water, then the water would resemble well water from the
chalk strata.
Now if a solution of lime-water, e. g. water containing 9 oz.
of lime, be united to a solution of water containing 16 oz. of
chalk and 7 oz. of carbonic acid, then the solutions will so act
on each other as to form % lbs. of chalk. Thus : —
Bicarbonate of lime ( lib. chalk =.,6oz.f Lime 9 oz. 1 . ,5 ^z )
in 400 gallons. ) ^^^^ iCarbonic acid 7 oz. / * f = 2lbs.
( Carbonic acid 7 oz.l s= 16 oz 1 ^^ Chalk.
Burnt lime in 40 gallons of water 9 oz. J ' '
In point of fact, only W of the chalk would be separated —
204 Purity of Water,
thus the water of 17^ degrees of hardness would remain of \\
degrees of hardness.
In practice, however, chalk water contains other hardening
matters besides chalk ; and consequently the softening can
rarely be effected below 2^ or 3 degrees. But the process
also appears to remove mechanically a great portion of any
organic matter in the water.
Where water has to be stored, or to remain exposed, as in
reservoirs, for any length of time, there is on the one hand
the great liability of soft water to absorb noxious gases, and
on the other the tendency with hard water to foster vege-
tation of various kinds. Waters from the new red sandstone
are worse even than the chalk waters in this latter respect.
Water softened by Clarke's process is comparatively free from
this objectionable tendency.
The general principles of water-supply may be stated briefly
as follows : —
1. To select the purest available source after careful analysis.
a. To filter the water, if necessary, in order to free it from
suspended matter and from dissolved organic matter.
3. To store it in covered tanks, and to raise it a sufficient
height for distribution by gravitation.
Water may be obtained from —
mountain ranges, which act as condensers,
rivers and streams ;
natural springs ;
wells artificially formed ;
impounding reservoirs ;
a combination of two or more of the sources named.
And water may be conveyed for distribution by means of —
open conduits (before filtration) ;
covered conduits, always, after filtration ;
cast-iron pipes under pressure, — where a district is to
be supplied with water.
^ Water containing much suspended matter is generally to be
Purity of Water. 205
avoided, but frequently the suspended matter may be removed
by filtration or simple straining.
As regards organic matter, it is the kind of organic matter
which is of importance.
The mere existence of organic matter either in solution or
in suspension is no proof of impurity. If water contains the
fresh juices of inoffensive plants, it would not be unwholesome.
But when these juices putrefy , or when water contains organic
matter, and especially animal matter, ready to putrefy, it
should be. avoided. ""
The question of analysis of water is beyond the scope of
this treatise, but a few remarks on the simplest facts connected
with examination of water may be useful.
The quality of a water can only be judged of from its con-*
stituents as a whole. The values of these constituents are not
their values absolutely, but their values relatively, and in con-
nection with the history of the water. Fifty grains of salt per
gallon may mean nothing ; five grains per gallon may mean
danger.
Care must be taken that the specimen of water to be
examined is a normal sample of the river or spring to be
tested, that the vessel it is placed in is cleaned and rinsed out
with some of the water to be tested. The water should
be collected from a spot where it is not subject to arti-
ficial disturbance, and in filling a bottle its mouth should
be immersed, if possible, from one to two feet below the
surface.
The bottle should be kept stoppered, and allowed to stand
for a day or two, exposed to light but not to evaporation, to
see whether vegetation or putrefaction is developed. It should
be in a temperature suited to vegetation.
If animalculae appear, they are an indication of nitrogenous
matter, and are one proof of the presence of substances
capable of putrefaction • a microscope is necessary to detect
the smaller forms of life.
2o6 Purity of Water.
Clearness and absence of colour in water is no certain indi-
cation of its being wholesome. The worst waters may be
clear, bright, and colourless. Colour as a companion to
chemical analysis may give to an experienced observer a clue
to the kind and quantity of organic matter present. Its
colour is best judged of through a tube 2 feet long, % inches
diameter.
If a water exhibits a bluish tint, or, say, appears nearly
colourless in the 2-foot tube ; if it, moreover, uses up very
little oxygen after standing for three hours in contact with
permanganate, the freedom of that water from organic im-
purity may be relied upon as certain.
If a water exhibits but little colour, or at most a slightly
yellow, or a greenish-yellow tint, but if the oxygen it uses up
is found to be large, such a water as a potable water is
suspicious.
If a water exhibits in the a-foot tube a decided peaty tint ;
if by experiment it is found to need a large quantity of
oxygen after standing for three hours ; knowing that peaty
matter acts as a reducing agent on permanganate, the quantity
of oxygen required, although far in excess of what was used
in the former case where there was an absence of colour in the
water, is not to be regarded with the same suspicion, peaty
matter not being injurious to health.
Water that will not bear the test of standing will, in most
cases, be rejected at once. If no other water can be obtained,
it ought to be used before putrefaction has set in, but this is
a great risk; the next best method is to wait until after
putrefaction has terminated.
An indication of the nature of organic matter in water may
be obtained by evaporating a small quantity of the water,
weighing the residue, and then burning it to drive off the
volatile matter, and comparing its weight before and after
burning. If the residue blackens in burning, it indicates
animal organic matter.
Ptirity of Water. 207
In considering whether organic matter comes from animals
or vegetables, the presence of common salt may in many
cases, with proper precautions, be found to be a nearly certain
guide.
We consume not less than 100 grains of salt a day. This
salt is thrown off daily. From all animals there is a large
outflow of salt. It is the constant accompaniment of the
animal living, or decomposing after death.
If much salt is found in water containing organic matter,
nitric acid will generally be found, and if not nitric acid, then
animal matter unoxidised.
In the case of dead animals organic matter is destroyed or
retained in the soil ; phosphates and other organic substances
are also retained. Salt is removed by water. Sewage
contains chlorides, and the amount of salt is the most certain
method of ascertaining the quantity of sewage which is or
has been present — assuming that there are no disturbing
causes.
Of course this test must be used with caution. Near the
sea the spray is driven many miles inland. In many districts,
where deposits of salt exist, wells and springs are saline.
Chlorides are also given out from manufactures.
Water containing chlorides to a great extent ought not to
be used without careful examination as to the source—three
grains per gallon of common salt coexisting with an excess of
nitrates is a cause of suspicion.
The average of the chlorides in the water of a district
having been obtained, any increase of common salt above the
average in a well situated in a camp or city, or near habita-
tions, is an almost sure test of impure drainage.
Although caution must be exercised in drawing conclusions
from the presence of chlorides, their absence is conclusive
against the presence of decomposed animal matter or ex-
creta.
Nitrates are common in small quantities. The amount
2o8 Purity of Water.
from atmospheric causes is very minute, but they are found
in water from manured land, in gardens, in wells near houses,
in towns, and in great abundance near churchyards.
If chlorides and nitrates are found together in water, it may
be assumed tRat animal matter has existed, or does exist, in
the water.
If there is much nitrous acid, it indicates recent organic
matter or oxidation going on.
The examination thus suggested would show the presence
or not of : — u.
I. Organic matter decomposed or putrid.
3. Organic matter readily decomposed and probably ready
to become putrid.
3. Organic matter slow to decompose, but still capable of
becoming putrid.
4. From th-e nitrites recent organic matter.
5. From the nitrates old organic matter.
6. Vegetable organic matter.
7. Animal organic matter.
In deciding on the quality of water the relationship which
each of its constituents bears to the others must be con-
sidered as well as the natural history and the physical
condition of the water. Any classification of waters founded
on a single factor in the chemical analysis of water is to be
accepted with great caution, however important that single
factor may be.
The general line of examination of waters can only be
indicated here.
The engineer in selecting a source of water-supply is so
deeply concerned in the question as to what is good water,
that these few practical hints on the subject may assist in the
consideration of the subject.
But whilst much knowledge is derived from a water
analysis, especially as to the waters which should be avoided,
it is necessary in the case of waters reported by analysis to
Purity of Water. 209
ft
be good, to be very careful to keep up a continuous examina-
tion of their sources, and to see that these are not liable to
contamination.
The sources of contamination of water arise at every step.
That which this country suffers from most largely is the
contamination of rivers by sewage.
With an increasing population over the districts which form
the water-sheds of rivers, this is inevitable.
The fact that sewage or other contamination is poured into
a river at a point high up on its banks is, however, no bar to
the water of that river being used at some spot lower down
for domestic purposes — ^the distance between the spot at
which contamination has been poured in and that at which
the water can be again used for domestic purposes, will
depend upon the nature of the bed of the river, the rapidity
of the current, and the temperature ; the effect varying with
the season, being much more rapid at a high than at a low
temperature.
This cannot be better illustrated than by extracts from the
Report of the Commission which reported on the pollution of
the River Seine at Paris in 1875 and 1876.
Above Paris the Seine presents a satisfactory appearance.
The sewers of Paris discharge into the river black foetid
streams, covered with layers of greasy matter, which ac-
cumulates on the sides of the river. These streams transport
particles of organic matter and debris, which are deposited as
gray and black mud on the banks, or else form shoals. This
mud is the seat of an active fermentation, throwing up in-
numerable bubbles of gas, which burst at the surface of the
water; the bubbles attaining sometimes in hot weather a
diameter of li metres (nearly 5 feet), dragging up the black
mud with them to the surface. Fish and plants cannot exist.
But as the river leaves these sources of pollution, it gradually
improves.
From Epinay to Argenteuil the water is still of a deep
P
2IO
Purity of Water.
colour, mud has disappeared, fish make their appearance.
Below Bezons a most abundant vegetation clothes both
banks, and large sheets of water-plants partly impede the
course of the river. At Meulan all visible sign of pollution
has disappeared, and the river is chemically pure.
The following table extracted from the report of the
Commissioners shows the chemical condition of the water :
Place.
Nitrogen not yet
transformed into vola-
tile ammoniacal salts,
or organic nitrogen.
Total nitrogen,
including volatile am-
moniacal salts.
Dissolved oxygen in
cubic centimetres per
litre of water.
Grammes per cubic
metres or zooo litres.
Grammes
per cubic metre.
Above Paris —
Bridge of Asnieres . . .
Tn Paris—
Clichy, below inter-
cepting sewer ...
St, Denis, below inter-
cepting sewer ...
Below Paris —
Meulan
Vemon
Grammes,
0.85
7.27
0.40
0.40
Grammes.
1-5
4.0
7.0
2.2
1.4
Cubic centimetres.
5-34
4.60
1*02
8.17
I0'40
The table explains the process which takes place.
The organic matters change into carbonic acid, water,
ammonia, sulphuretted hydrogen, and different mineral sub-
stances. This change implies an absorption of oxygen from
the gases dissolved in the water, and a production of mineral
nitrogenous bodies.
As long as the water contains such matters susceptible of
fermentation, it is unfit for use. When fermentation is ac-
complished, and the organic matter has passed into the
state of mineral matters inoffensive in themselves, the water
presents ,a disappearancQ of nitrogenous organic matter.
Purity of Water. 2 1 r
replaced by nitrogenous mineral matter, by ammonia. The
dissolved oxygen in the water is used up, but may be
restored by movement, such as is caused by the flow of
the stream, or more rapidly by agitation, as for instance in
passing over a weir, and thus the water can be rendered
fit for drinking, •
It will be seen from this that although a river may have
received sewage at one part of its course, there is some point
below at which it will still become fit for use.
There are other and more occult sources of contamination.
All water proceeds from evaporation and rainfall. The
rain which falls on impervious strata passes from the surface
into rivers, whilst water which falls on pervious strata passes;
into the ground.
When this water, in its passage through pervious strata,
meets with an impervious bed, it is arrested in its course ;
and if the impervious bed dips down and forms a basin, then
the water will remain in a subterranean reservoir accessible
only by wells.
Where the impervious strata which underlie the pervious
strata crop out at the surface, the water flows gradually
down as an underground river, to pass out at the lowest point
in springs.
An examination of the water-level of different districts
seems to show that this general water-level forms an inclined
plane, rising from the natural vent or outfall.
But the course of this underground river depends on the
inclination of the water bearing and underlying impervious
strata, and not on the form of the surface.
Taking the water-levels of a line of wells at right angles to
the outfall, be it in a river or in springs, it has been found
that in the chalk the inclined plane of the surface of under-
ground water rises at a rate of not less than ten feet per
mile^; in the boulder strata of Norfolk it appears to vary
* Clutterbuck.
P %
212
sPurtty of Water,
frorii three to a hundred feet per mile ; and in certain of the
tertiary beds it is about five feet per mile ^.
Of course this inclination varies with the head of water
and the porosity or permeability to water of the material,
Mr. Roberts, of Liverpool, found by experiments in the
new red sandstone of average coarseness of that district, that
the following quantities of water passed per hour through a
square foot of the sandstone loi inches in thickness : —
With a pressure of lo lbs. to square inch, 4i gallons
^o « « 7i
4<5 „ „ 19
which showed the increase to vary in a direct ratio with the
pressure.
The level of the subterranean sheet of water, moreover,
rises and falls with the quantity supplied by rainfall ; thus,
in wet seasons, the water-level approaches near to the sur-
face, and in dry seasons it recedes. Mr. Baldwin Latham
has shown the effect of this change in contaminating the
water supply at Croydon. (Fig. 36.)
79
}>
»
»
± 8 9 S S e 7 6 8 JVfi2M
Fig. 36, Section of water-level in chalk near Croydon.
Croydon has been drained effectually, and the water-supply
IS obtained from springs at some distance off in the chalk.
^ Baldwin Latham.
Purity of Water. 2 1 3
In the dry seasons the supply was excellent; in wet
seasons fever was found to prevail, which was attributed to
the water. The cause of this was explained by the fact
that in dry seasons the level of the water was far below
any subsoil contamination; but that, in 3 wet season, the
water-level of the underground river rose up to the level
of cesspits which were not impervious, manure heaps, and
other sources of contamination, and thus became contami-
nated with the contents.
i^S?
^S^^^^^^S^F^^^^S^^&L^- » ''" ,< ^^ --r^=
There are, however, many causes of contamination of water
which are much more obvious.
In a porous soil, the vicinity of a cesspit is a frequent cause
of danger. Figs. 37 and 38 show how fluctuating may be
the danger in such cases.
In one case {Fig. 37) the flow of underground water is
from the cesspit to the well.
Whilst the ordinary level of underground water prevails.
214
Puriiy of JVater.
there would be nothing to indicate the danger; but upon
an excess of rainfall occurring, by which the current of
underground water was altered, then the well would become
polluted, and sickness break out, to cease probably on a
fresh change of conditions.
In the second case (Fig. 38) the flow of underground
water is from the well to the cesspit, and in this case there is
not the same imminent danger of pollution as in the former
instance.
The pollution of the water may occur in its transit from
the source of supply to the consumer. The London Water
Companies have sometimes had the water polluted by pass-
ing it through iron mains calked with hemp, when the hemp
has become a cause of injury to the water.
The question of water-supply would require a treatise to
itself ; a few practical hints are all that can be given here.
The quantity of water for the civil population cannot be
assumed at less than 15 gallons per head per day ; for infantry
ii2 gallons per head per day, for cavalry 20 gallons per head
per day, in barracks.
An Artesian well (Fig. 39) is a well sunk through imper-
vious strata, in which there is no water, into pervious strata
Surface
f77» m J' J' . . 4 yi . -^ 3 . ,
Fig. 39. Artesian Well.
which derive their supply from a water-shed area at a dis-
tance. Thus, in London, wells are sunk through the London
clay to derive their supply from the chalk. The water in the
Purity of Water. 215
chalk comes from the water which falls on the chalk hills
surrounding the London basin. Deep well water is generally-
very good and palatable water.
In porous soils water must generally be obtained froni
surface wells.
A spring is the lowest point or lip in the stratification of an
underground reservoir 'of water. A well sunk in such strata
will most probably furnish, besides the volume of the spring,
an additional supply of water.
Well water will vary in purity according to the nature
and amount of the soluble matters contained in the ground
from which the well derives its supply.
Shallow wells are always liable to pollution from vegetable
matter, or animal matter, in or on the surface soil.
In deep wells differences have been observed in the purity
of well water, according as the water was taken from the
surface by dipping, or was pumped from the bottom of the
well. In one case, where the depth of water was over 50 feet,
the surface water was found to be yellowish in colour, much
harder, and more contaminated with organic impurities than
that from the bottom of the well, as if a layer of lighter water
from the surface drainage floated on the spring water below.
In another case the solids per gallon amounted to 66'%2^ grains
in the bottom water of a well and to 3 grains only in the
surface water.
Such differences are often constant. Exhaustive pumping
in wells may be injurious to the water ; especially in wells in
the vicinity of the sea, when the brackish water usually kept
back by the lan^ water may be drawn in.
Norton's tubes are useful for ascertaining the quantity of
subsoil water, and fof drawing the supply from a certain
depth. They are easily applied ; but the supply from each
has necessarily a limit.
In camps it may frequently be necessary to resort to a
surface supply of Water.
2i6 Purity of Water.
The following are a few temporary expedients for camp
purposes of water supply. ■
Where the water was near the surface, one system pursued
by the Turks in the Crimean war was to select a site near their
camp where the surface was clean, and dig a hole and place
in it a barrel {Fig. 40), in the bottom of which holes had been
bored, so as to ensure that water frdm the deepest part of
the hole should alone come into the
barrel. If they wanted further fil-
tration, they got a smaller barrel,
and bored holes in the sides as
high as was desired, and they then
placed the smaller barrel in the larger
one, ramming sand in below and all
^"'''^Fig."^! ^*"' '°""d so as to bring its top to the
level of the top of the first barrel,
and thus forming an upward filter of sand through which the
water passed.
The Russian plan, where brushwood was obtainable, was to
make a large gabion four or five feet in diameter, some 10 or
12 feet long, and then to dig the well and drop this gabion
into it. This formed a temporary casing, which answered its
immediate object.
For wells of any degree of permanence, care is necessary to
ensure that the surface water for a certain distance round the
well should not pass back into it, for the surface near a well
is always liable to pollution.
In deep wells, i. e. wells in which the water of the requisite
purity is only found at a considerable depth, the surface soil
water should be cut off from the deep water by carefully
casing the well and puddling behind the casing above the
water level, so as to prevent surface water from trickling
down the sides.
Surface wells in porous strata should be lined with puddle
behind the steyning to the full depth, or in wells beyond la
Purity of Water. 2 1 7
to 15 feet in depth, then to that depth at least, so as to
ensure complete filtration of the surface water which passes
into the well. The surface round the well should also be
puddled, sloped away from the well, and paved, so as to
prevent the dirty water which is thrown down near the well
from finding its way back again. (Fig. 41.)
The distance to which this preparation of the surface
should be carried round the well depends on the depth of
the well ; with a deep well, in
which there would be a con-
siderable depth of soil through
which the surface water would
have to pass before it reached
the well, an extensive surface
covering would not be necessary;
whilst with a shallow well, by
extending the area of surface
puddling, the amount of fil-
. .... J- Fig. 41. ShflUowWell.
tration to which the surface
water would be subjected before it reached the well may be
materially extended.
The tube lining of the well should be carried up to at least
two feet abovethe surface, so as to prevent surface impurities
from falling in. The well should be covered as a protection
against dead leaves, &c.
For keeping well-water clean, it is preferable that it should
be drawn up by a pump. In the use of buckets impurities fre-
quently fall in. If not a pump, then an iron chain and bucket,
because they can be kept cleaner than rope and wood.
In some cases there is advantage in the aeration which the
water obtains by being exposed to the air. In such cases,
closing the well and drawing water by pump has rendered
the water undrinkable.
Where a river flows through a valley over porous substrata,
sinking a well or wells in the strata within the influence of
2i8 Purity of Water.
the river filtration is a cheap and ready niethod of obtaining
river water naturally filtered. The tops of wells so situated
must be carried above the level of extreme floods.
If a single well on a river bank does not produce sufficient
water, or if the; subsoil is clay, impervious to water, trenches
may be excavated parallel to the river or stream, in which
trenches perforated earthenware pipes may be laid, leading to
a well or wells. The trenches above such pipes should be
filled in with fine assorted gravel, charcoal, and sand, so as to
form a filtering medium within the reach of the dry weather
flow of such stream or river. These trenches should not be
less than six feet deep to the top of the pipes.
At Florence the new water-supply for the town is derived
from channels nearly a mile long, carried by the side of and
below the level of the Arno.
Natural springs may be utilised by storing the water in a
reservoir which will contain the flow of one entire day, or
of a longer period.
All reservoirs and tanks should be constructed to prevent
infiltration of water from the soil, the sides and bottom should
be lined with puddle, faced with brick or masonry walls, and
coated with cement. Reservoirs may be covered in to
protect the water from contamination. In case of peaty
waters aeration is beneficial ; and in such cases it may be
advisable to draw off" the upper film of water for use.
In positions where there is a difficulty as to wells, springs,
or streams, dependence must be placed on rainfall. Where
water is to be collected from rainfall, great care is requisite
in order to keep perfectly clean the surfaces on which it falls,
as well as the conduits to the reservoirs and tanks.
When rain water is collected from roofs, the first washings
of the roof should not be collected.
Rain water is not agreeable to the taste until it has been
stored in the ground, where it absorbs carbonic acid gas.
The rain water from roofs should be first collected in a
Purity of Water. 219
settling tank, of a sufficient area to allow the heavier sedi-
ment to be deposited; it should then be passed through a
gravel or coarse sand strainer into the tank or cistern for
use. It is customary in parts of Italy to provide three
receptacles. The rain water is received and allowed to settle
in the first, it is strained off into the second, where it is
retained if possible for a year, and then passed into the third
for use. The settling tank and the strainer should be cleaned
out frequently.
In the case of porous strata of clean sand or gravel, where
sufficient ground can be set apart, and where military or
cheap labour is available, water may be stored by excavating
an area, of a size calculated on the minimum rainfall, to a
depth of five or six feet, and paving the bottom with tiles, or
impervious material such as puddle, cement, or asphalte,
sloped down towards one comer, and lining the sides with
puddle, and then filling in the whole again with the porous
material of the ground. A pump could be fixed in the
lowest corner.
The surface should be covered with grass or shrubs, and kept
free from impurities. By these means a valuable reservoir
would be formed, which would keep the water cool.
All water, before being stored in tanks, from which it is to
be pumped direct for use, should be passed through a filter ;
every rain water storage tank should have its filter.
For filters on a large scale, sand is the simplest material.
It not only operates as a strainer, but the surfaces of the
particles of sand serve more or less to attract solid matter
brought within range of their attraction. It has been estimated
that a cubic yard of sand would contain an area of surface in
the particles of about ^2,500 square yards.
A sand filtering-bed should have a thickness of about
two feet of sand at the top, under which should be placed four
layers of gravel, each six inches thick, the first of the size of
shot, the next of peas, the third of beans, the fourth the size
220 Purity of Water.
of walnuts; the rate of filtration should not exceed two
gallons per superficial foot per hour.
The surface soon becomes clogged, and the rate of filtration
decreases ; the upper film of sand should then be removed and
a fresh layer put on.
Filtering beds of sand are stated to filter the water less
efTectually when first constructed ; the filtration afterwards
becomes more perfect, and remains so until the lower stratum
of sand is filled up with organic matter. The filtering bed
should then be renewed. The duration of a filtering bed in
fairly constant use should not exceed two years. If the bed
were left dry at intervals, a somewhat longer period might
be afforded before renewal.
The sand filter acts not only mechanically, but it will to
some extent remove matters in solution.
Filters for domestic purposes were experimented on by
Dr. Parkes. He showed that a sand filter has considerable
purifying power when first used, but that it clogs rapidly. The
sediment stops mainly on the surface, and thus diminishes its
*
filtering power; this can be restored for a certain time by
scraping off a small film of the top surface of the sand.
Magnetic oxide of iron may be usefully added to a sand
filter where there is much organic matter. It increases the
oxidizing power of the filter, and renders it more effective for
destroying organic matter.
Sponges are useful with sedimentary waters; they arrest
more than their own weight of solid matter, and are very
easily cleaned.
One of the best filtering mediums is animal charcoal. The
charcoal, in consequence of the very large surface arising from
its porosity, undoubtedly has great power as a mechanical
filter. It has been contended by some chemists that the
organic matter which passes into it becomes oxidised. On
this point, however, the evidence is not conclusive.
Spongy iron appears to be an active agent, not only in
Purity of Water. 221
removing organic matter from water, but in reducing its
hardness and altering its character when water is filtered
through the spongy material.
Filters retain the impurities which are present in the water,
and at first the outflowing stream is materially purified ; but
the retention of the impurities in the filter becomes very soon
a source of danger of itself.
The pores become filled with the dead bodies of the
organisms which were living in the water, and the water
passing through may become after a time more dangerously
polluted than it was before it entered the filter.
Filters must, therefore, be frequently and thoroughly
cleansed by washing the materials of which they are com-
posed, and by exposing these materials to the air, so as to
cause any remaining impurities to be oxidised.
A filter with sponge to arrest the sediment, so arranged
that the sponge can be frequently cleaned, and a porous
filtering medium so arranged as to have a free exposure to
the air when water is not actually passing through, would be
the best form of domestic filter.
After filtration water should be kept in covered receptacles
for use.
The storage and distribution of water is the next con-
sideration.
The best position for keeping water is in tanks under-
ground, assuming always that it is not in proximity with
sources of impurity. In the ground it will retain an even
temperature, and will take up carbonic acid gas, which makes
it pleasant to the palate. When stored in cisterns above the
ground-level, where its temperature is necessarily variable,
much danger may ensue from its power of absorbing gases,
For instance, on a warm day, the water becoming warm,
gives out the oxygen or other gases it contains; at night,
when it cools down, its capacity for absorbing gases is much
increased ; and if there are impure gases near, such as sewer
222 Purity of Water.
gas^ or ammonia from dung heaps or manure heaps, it will
absorb them in large quantities, and thus become dangerously-
polluted.
The system of water-supply which minimises this source of
danger is to be preferred. Thus well-water was observed to
have a maximum temperature of S^*^^ and a minimum tem-
perature of 5o«5°, or a mean of 51° during the year in the same
locality. The water supplied from mains had a maximum
temperature during the year of 64-8°, a minimum temperature
of 39*7°, and a mean temperature of ^%*%1^ ; and the water in
cisterns above ground varied from 7i'5® maximum to 33'6o*'
minimum, with a mean of 5iZ'55°. Thus whilst the range of
temperature of the well-water was only to 1°, the range of the
water in the cistern was nearly 38**,
There is danger from the use of cisterns unless frequently
cleaned, for the cistern becomes a place of deposit for any
impurities which there may be in the water ; especially if the
cistern is left unused for a time ; and thus, like the filter when
not cleaned, cisterns may render the fresh water which comes
into them impure.
Moreover, the supply of water to cisterns is necessarily
intermittent, and when cisterns have been filled, and the pipes
are emptied of water, cases have occurred in which impure
gases have been drawn into the pipes, and have been taken up
by the water when it was again turned on into the pipes,
A case occurred in which a town council, in order to econo-
mise the laying of pipes, carried them in the sewers. A
severe epidemic of typhoid fever occurred. This was accounted
for by the assumption that sewer gas was drawn into the
pipes, either through the joints or by diffusion through the
pores of the metal.
On these grounds the constant service, in which the pipes
are always filled, is preferable to the intermittent supply.
As water will readily absorb foul gases, and may become
poisonous, the possibility of contamination from foul air should
\
Purity of Water. 223
be prevented. Hence any overflow or waste-water pipe from
a service reservoir or tank should deliver the water at an open
end into a channel, and be thence conducted into the covered
sewer, or drain, so as to prevent gases from the sewer rising
back through such overflow or waste-water pipe to the water
in the reservoir or tank.
Water conduits should be laid at such depth and be so
covered with earth as to prevent the water becoming heated
unduly by the rays of the sun, or being injuriously affected by
frost in winter. This depth may be considered to be not less
than two or three feet.
All covered reservoirs and tanks should be ventilated, and
so situated £is to be easily emptied, inspected, and cleaned.
All supply-pipes should be arranged in such manner as to
allow of easy inspection and subsequent repairs. Stop-taps
should be placed betwixt the water main and the building in
all cases, so as to allow of the isolation of any line of service-
pipe for repairs.
All house service-tanks and service-pipes should be fixed in
such manner as to be carefully protected from frost, and so
that the best rooms shall not be flooded on the occurrence of
leaks or overflows. When protected by wooden casings, the
front of the casing should be made to open easily.
The distribution of water in camps should invariably be
placed under inspection, and under the charge of some person
who should be responsible for not allowing waste or pollution.
With this object the general dipping of buckets into a well
should be prevented.
If a pump is not fixed, there should be one man made
responsible for raising the water out of the well. He should
pour it into a box or reservoir in front provided with taps, out
of which all who come for water should draw without confusion
or fouling of the well with dirty buckets.
The surface of the ground near any place where water is
obtained should, if possible, be paved, or else it will soon
224 Purity of Water.
become a mass of mud. This is especially desirable with
horse-troughs.
In making troughs for watering horses care should be taken
to supply each trough independently of the neighbouring
troughs. It has been often the practice to place the troughs
in a line, and let the overflow of the first fill the second, and
so on ; but the water of a trough becomes fouled by the horses
drinking in it, and consequently the overflow from the upper
troughs conveys nothing but polluted water into the lower
ones.
No vessel to convey water for drinking purposes for human
beings should under any circumstances be allowed to be
dipped into a trough used for watering horses.
CHAPTER XVI.
REMOVAL OF REFUSE.
A THEORETICALLY perfect system of refuse removal would
be one where a large volume of rapidly flowing water received
the whole refuse, and carried it away, before it had time to
decompose, to a large river not used for drinking purposes, and
thence to the sea ; but this is generally unattainable, and it
would leave the waste matter unutilised.
Refuse from dwellings falls under the heads of ; —
1. Ashes.
2. Kitchen refuse.
3. Stable manure.
4. Solid or liquid ejections.
5. Rain water and washings of passages, stables,
yards, and pavements.
The first three of these should be removed by hand labour ;
it is only to the two last that the term sewage is applied.
To arrive at a clear conception of what the problem is, it
must be remembered first, that even where a water carriage
system prevails in any town, some plan of removing house
refuse, ashes, and dust — some 'dry system* of collection —
must also be in force, and secondly, that an ordinary house-
hold of, say, six persons, enjoying a proper water supply, will
consume for all purposes from 15 to ao gallons per head per
Q
226 Removal of Refuse.
diem, or a total daily quantity of from 90 to \%o gallons, which
must necessarily be fouled in its use, and pass away from the
house, laden with dangerous impurities. If earth-closets are
used instead of water-closets, a certain quantity of water,
perhaps as much as four or five gallons per head may be
saved, but there will be still from 10 to 15 gallons of water
fouled with grease, soapsuds, vegetable refuse, and other
materials of a highly putrescible kind, which must necessarily
pass away and be disposed of at the outfall.
Thus some system for the removal of foul water is absolutely
necessary in every town, and the Rivers Pollution Com-
missioners, in their First Report, after a careful comparison of
thirty-one towns, in fifteen of which the midden system
prevailed, while sixteen were water-closet towns, came to the
conclusion that it mattered little, as regards the degree of
pollution in the sewer water, whether a system of interception
of the excreta was practised or not.
Hence, with the dry conservancy system, there must be the
removal of sewer water.
With the water carriage system the removal of ashes, refuse,
and stable-yard manure has still to be provided for ; but the
removal of ashes and stable yard manure is a much simpler
matter than the removal of excreta.
The great principle to be observed in removing the solid
refuse is that every decomposable substance should be taken
away at once.
This is especially necessary in warm climates.
The principle may, however, be applied in various ways to
suit local convenience. In open situations, exposed to cool
winds, there is less danger of injury to health from decom-
posing matters than there would be in hot, moist, or close
positions. In towns in warm climates all refuse should be
removed daily from both the house and its enclosures.
In the country, generally, there is less risk of injury than in
the close parts of towns. These considerations show that the
Removal of Refuse. 227
same stringency is not necessarily required everywhere.
Position by itself affords a certain degree of protection from
nuisance. The amount of decomposing matter usually pro-
duced is also another point to be considered. A small daily
product is not, of course, so injurious as a large product.
Even the manner of accumulating decomposing substances
influences their effect on health. There is less risk from a
dung-heap to the leeward than to the windward of an in-
habited building.
The receptacles in which refuse is temporarily placed should
never be below the level of the ground.
If a deep pit is dug in the ground, into which the refuse is
thrown in the intervals between times of removal, rain and
surface water will mix with the refuse and hasten its decom-
position, and generally the lowest part of the filth will not be
removed, but will be left to ferment or putrefy, and the
presence of this fermenting mass will tend to promote the
decomposition of the fresh refuse added to it.
Even the daily removal of refuse entails the necessity of
places for the deposit of refuse. In the selection of these the
following conditions should be attended to : —
I. That the places of deposit be sufficiently removed from
inhabited buildings to prevent any smell being perceived by
the occupants.
%. That the places of deposit be above the level of the
ground— never sunk in the ground. The floor of an ash-
pit, or dung-pit, should be at least three inches above the
surface-level.
3. That they be lined with non-porous material. That the
floor be paved with square setts, or flagged, and drained.
4. That they be protected from rain and s,un, but open to
the air.
5. That a space be paved in front, so as to prevent the
traffic, which takes place in depositing the refuse or in
removing it, from cutting up and polluting the surface.
228 Removal of Refuse.
A moveable iron box is a good receptacle for kitchen waste.
For stable-yard refuse, the mcJveable wire-work grating in use
in London is safer than any form of dung-pit.
In camps the disposal of manure and offal requires great
care ; burning, unless carefully done, may give rise to much
nuisance ; burying at a safe distance is generally the most
advisable method.
The disposal of the solid or liquid ejections, which constitute
what is generally termed sewage must next be considered;
and before entering upon the general question, a few of the
rules which govern temporary emergencies in camps may be
mentioned.
A camp unprovided with latrines is always in a state of
danger from epidemic disease.
One of the most frequent causes of an unhealthy condition
of the air of a camp is, either neglecting to provide latrines, so
that the ground outside the camp becomes covered with filth,
or constructing the latrines too shallow, and exposing too
large a surface to rain, sun, and air. Latrines should be so
managed that no smell from them should ever reach the
men's tents ; to ensure this, very simple precautions only are
required.
1. The latrines should be placed to leeward with respect to
prevailing winds, and at as great a distance from the tents as
is compatible with convenience.
2. They should be dug narrow and deep, and their contents
covered over every evening with at least a foot of fresh earth.
A certain bulk and thickness of earth are required to absorb
the putrescent gas, otherwise it will disperse itself and pollute
the air to a considerable distance round.
3. When the latrine is filled to within two feet six inches
or three feet of the surface, earth should be thrown into it,
and heaped over it like a grave to mark its site.
4. Great care should be taken not to place latrines near
existing wells, nor to dig wells near where latrines have been
Removal of Refuse. 229
placed. The necessity of these precautions to prevent wells
becoming polluted is obvious.
Screens made out of any available material are, of course,
required for latrines.
This arrangement applies to a temporary camp, and is only
admissible under such conditions.
A deep trench saves labour, and places the refuse in the
most immediately safe position ; but a buried mass of refuse
will take a long time to decay ; it should not be disturbed,
and will taint the adjacent soil for a long time. This is of
less consequence in a merely temporary encampment, whilst
it might entail serious evils in localities continuously in-
habited.
The following plan of trench has been adopted as a more
permanent arrangement in Indian villages, with the object
of checking the frightful evil of surface pollution of the whole
country, from the people habitually fouling the fields, roads,
streets, and watercourses.
Long trenches are dug, at about one foot or less in depth,
on a spot set apart, about rzoo or 300 yards from dwellings.
Matting screens are placed round for decency. Each day the
trench which has received the excreta of the preceding day is
filled up, the excreta being covered with fresh earth obtained
by digging a new trench adjoining, which when it has been
used is treated in the same manner. Thus the trenches are
gradually extended, until sufficient ground has been utilised,
when they are ploughed up and the site used for cultivation.
The Indian plough does not penetrate more than eight
inches, consequently if the trench is too deep, the lower
stratum is left unmixed with earth, forming a permanent
cesspool, and becomes a source of future trouble.
It is to be observed, however, that in the wet season these
trenches cannot be used ; and in sandy soil they do not answer.
This system, although it is preferable to what formerly
prevailed, viz. the surface defilement of the ground all round
230 Removal of Refuse.
villages, and of the adjacent water courses, is fraught with
danger, unless subsequent cultivation of the site be strictly
enforced, because it would otherwise retain large and increas-
ing masses of putrefying matter in the soil, in a condition
somewhat unfavourable to rapid absorption.
These arrangements are applicable only to very rough life
or very poor communities.
In permanent camps and barracks, and in villages where
the houses or cottages are close together, and where therefore
sufficient garden ground cannot be allotted to each to allow of
the refuse being absorbed, which is especially the case with
large Indian villages, some one of the methods adopted for
town conservancy hereinafter described would usually be found
applicable.
Midden, Pail^ and Dry Earth systems.
Moveable apparatus, such as middens, pails, or dry earth
closets all involve the retention of the excreta for some period
of greater or less duration, as contradistinguished from the
immediate removal which takes place when water carriage is
used. Moreover the weight of the tub, pail, or receptacle in
which the excreta are removed has to be added to the weight
of the refuse to be carried away, whilst in the water carriage
system the water itself is the vehicle of transport.
There are numerous towns, and innumerable villages and
cottages, where the midden closet or privy with a fixed re-
ceptacle still prevails.
In its old form the receptacle consists of a pit with sides of
porous materials, permitting free soakage of filth into the
surrounding soil, capable of maintaining the entire dejections
from one or more houses for months or years, uncovered and
open to wind and rain and sun, undrained and difficult of
access for cleansing.
The first improvement was to provide a cover to keep out
the wet ; the next, to provide a drain for excess of liquid, and
Removal of Refuse. 231
to make the sides and bottom of the pit impervious ; the next,
to deodorise the contents with ashes, or some other cheap
deodoriser. The next important improvement was to reduce
the size to a mere space behind the seat, formed of some non-
porous material, such as glazed brick, and arranged for easy
cleaning from the back. The small size prevents the retention
in the vicinity of the dwelling of a large mass of putrescent
matter. Privies of this class are, however, inadmissible except
in detached positions away from dwellings, as for instance at
the end of a cottage garden in the country ; but where used,
the floor of the privy should be raised, so that the seat may
be high enough to admit of the floor of the receptacle being
on or a little above the level of the ground, with a slightly
raised edge to prevent any liquid flowing over. The recep-
tacle should also receive dry refuse and ashes, which help to
deodorise the contents and soak up the liquid ; and the
receptacle should have a cover to prevent rain falling into it, but
so placed as to allow of the circulation of air under the cover.
The next transition from this was to a moveable receptacle.
Of this type the simplest arrangement is a box placed under
the seat, which is taken out, the contents emptied into the
scavenger's cart, and the box cleansed and replaced.
A further alteration is the separation of the solid and liquid
excreta ; a system which has not hitherto attained to much
practical application.
The difficulty of cleaning the angles of the boxes led to the
adoption of oval or round pails. (Figs. 4fl and 43.) The pail
is placed under the seat, and removed at stated intervals, or
when full ; some form of deodorising material is thrown in daily.
In the north of England the arrangement generally is that the
ashes shall be passed through a shoot, on which they are
sifted — the finer fall into the pail to deodorise it, the coarser
pass into a box, whence they can be taken to be again burned
— whilst a separate shoot is provided for kitchen refuse, which
falls into another pail adjacent. (Figs. 44, 45, 46, and 47.)
233 Removal of Refuse.
Excrtmeol Paitfiia. ^"'tl' li^".
ExcrtmtKt Pail tinffy, rtadyfor ust.
Fig. 41. 43. Hie Rochdale Pail.
EltMlk^i n rant.
Sictional EUvatieK-
Flan aiDoi Privy Smi. Plan rfPrinf Fleer.
Fig. 44. 45, 46. 47. Closet with pail and refuse box.
Removal of He/use, 233
The general arrangement is for the floor of the privies to be
somewhat raised, so that the space underneath the seat in
which the tub is placed may be at or somewhat above the
level of the ground, so as to be easily cleaned.
A door gives access to the space under the seat, and when
the tub is removed it is at once covered with a lid and placed
in a van, while a clean tub, having in it a small supply of
disinfecting fluid, is substituted for the full one taken away.
The van holds twenty-four tubs ; each van making several
journeys a day.
The Goux system, which has been in use at Halifax,
consists in lining the pail with a composition formed from
the ashes and all the dry refuse which can be conveniently
collected, together with some clay to give it adhesion. The
lining is adjusted and kept in position by means of a core or
mould, which is allowed to remain in the pails until just before
they are about to be placed under the seat j the core is then
withdrawn, and the pail is left ready for use.
Ijued Pail used for Godi System.
The liquid which passes into the pail soaks into this lining,
which thus forms the deodorizing medium.
The proportion of absorbents, in a lining three inches thick,
to the central space in a tub of the above dimensions, would
be about two to one ; but unless the absorbents are dry, this
proportion would be insufficient to produce a dry mass in the
tubs when used for a week, and experience has shown that
after being in use for several days the absorbing power of the
234 Removal of Refuse.
lining is already exceeded, and the contents have remained
liquid.
There would appear to be little gain by the use of the
Goux lining as regards freedom from nuisance, and though it
removes the risk of splashing and does away with much of
the unsightliness of the contents, the absorbent, inasmuch as
it adds extra weight which has to be carried to and from
the houses, is rather a disadvantage than otherwise from
the manurial point of view. "
The great superiority of all the pail or pan systems over
fixed middens, such as formerly prevailed, is due in the first
place to the fact that the interval of collection is reduced to
a minimum, the changing or emptying of the receptacles
being sometimes effected daily, the period never exceeding
a week ; and secondly to the receptacles for the refuse being
independent of the structure, and therefore capable of easy
periodical renewal when the material becomes saturated.
In the ordinary pail system, the plan of deodorising the
material whilst the pail is in use is scarcely resorted to, from
the trouble and expense it occasions ; and probably the best
known contrivance for deodorising the excreta immediately
after they fill into the receptacle, is Moule's Earth-closet, in
which advantage is taken of the deodorising properties of
earth. Many modifications of this system are in use.
Dry earth is a good deodoriser; li lbs. of dry earth, of
good garden ground or clay, will deodorise each excretion.
A larger quantity is required of sand or gravel. If the earth
after use is dried, it can be applied again, and it is stated that
the deodorising powers of earth are not destroyed until it has
been used ten or twelve times.
This system requires close attention, or the dry earth closet
will get out of order, and the best dry closet is liable to a
peculiar smell, which becomes very objectionable when the
closet is not properly cleansed.
As compared with water-closets, the earth-closet is cheaper
Removal of Refuse. 235
in first construction, and is not liable to injury by frost ; and
it has this advantage over any form of cess-pit, that it ne-
cessitates the daily removal of refuse.
On the other hand, the dry earth system is much more
expensive than the pail system.
The dry earth system, though applicable to separate houses,
or to institutions where much attention can be given to it, is
inapplicable to large towns from the practical difficulties
connected with procuring, carting, and storing the dry earth.
The pail system, which is in use in various ways in the
northern towns of England, and in the permanent camps to
some extent at least, is more convenient as well as more
economical than the dry earth system, where the removal of
a large amount of refuse has to be accomplished.
The value of the manure depends on its bulk in relation to
the distance it has to be carried.
If the manure is highly concentrated, like guano, it can
stand a high carriage. If the manuring elements are diffused
through a large bulk of passive substances, the cost of the
carriage of the extra, or non-manuring elements, absorbs all
profit If a town, therefore, by adding deodorants to the
contents of pails, produces a large quantity of manure, con-
taining much besides the actual manuring elements — such as
is generally the case with dry earth — as soon as the districts
immediately around have been fully supplied, a point is soon
reached at which it is impossible to continue to find pur-
chasers in consequence of the high cost of carriage.
According to theory, the manurial value of dejections per
head per annum ought to be from 8j. to loj. And if the pail
system is to be commercially advantageous, the liquid and
solid dejections must be collected without admixture of
foreign substances.
General Scott has devised a plan by which he hopes to
effect this.
He mixes the contents of the pails with lime, arid distils
236 Removal of Refuse.
the mixture in a close boiler, so as to draw off four-fifths of
the ammonia.
The ammonia thus evaporated is passed into a tank filled
with sulphuric acid, and thus sulphate of ammonia is obtained
in a crystallised state fit for the market.
The residue, after being mixed with superphosphate and
dried, is ready for sale as manure.
In a sanitary point of view the pail or tub system has an
enormous advantage over the old midden or cess-pit system,
in the facility with which the excrementitious matter is
removed, without soaking into the ground or putrefying in
the midst of a population.
There is no doubt that in some parts of India, where the
water supply is often not plentiful, and the question of sewage
removal presents many difficulties, a systematised pail system
would afford great advantages.
Pneumatic System for the Removal of Excreta.
Instead of the removal of the excreta, as just described, by
the pail system, there is in Paris, in Florence, in Philadelphia,
and in other foreign towns, a pneumatic system in operation.
The water-closet refuse is passed into close cess-pits, from
which the contents are removed at frequent intervals. To effect
this, in Paris a large cylinder, in Philadelphia a series of barrels,
are brought on a cart ; a tube from them is connected with the
cess-pit, the air is then exhausted in the barrel or cylinder
by means of an air-pump, and the contents of the cess-pit
drawn through the tube by the atmospheric pressure into the
cylinder or barrels.
A plan which is practically an extension of this system has
been introduced by Captain Liernur, in Holland.
He removes the foecal matter from closets, and the sedimen-
tary products of kitchen sinks by pneumatic agency. He places
large air-tight tanks in a suitable part of the town, to which
Removal of Refuse. 237
he leads pipes from all {he houses. He creates a vacuum in
the tanks, and thus sucks into one centre the foecal matter
from all the houses.
The mode of action is briefly as follows : — These tanks are
in communication, by means of pipes, with small tanks in
each street, so arranged that the vacuum in the central tanks
can at will be extended to any given street reservoir.
Each of these street reservoirs is the centre of a small
drainage system of houses, independent of all others, and the
foecal matter out of those houses is drawn into it by means of
the vacuum, created in the manner described, after which the
matter is at once despatched to the main building by means
of the same pipe that first conveyed the air. The closets are
connected with a main pipe lying in the street, by means of
branch pipes, somewhat like the mains and branches of water-
works. Each main has, however, only one stop-cOck, and
when this is turned all the closets connected with it empty
themselves at once through the main pipe into the street
reservoir.
The manipulation is as follows : — The air-pump engines
maintain throughout the day a vacuum in the central tanks,
and hence also in the tubes, extending the vacuum into the
street reservoirs. A couple of men perambulating the town,
visit each reservoir in turn once a day, and discharge into
them, by opening the stop-cocks of the mains, the closet
matter of all the houses belonging to the particular section
connected with the reservoir ; after which, before leaving, they
dispatch the whole to the central building by simply opening
the stop-cock of the communicating pipe.
This system is extremely ingenious ; it is in operation at
Dordrecht and Leyden, and has been experimented on at
Amsterdam ; but from recent reports it does not appear
probable that it will be adopted by other towns.
In a sanitary point of view it would seem primd facie to
present some questionable features.
538 Removal of Refuse.
No current of air, however rapid, can be so rapid as the rate
at which gases diffuse themselves ; there must be always some
film of filth left on the sides of the pipes, however perfect
the vacuum ; it is moreover stated that in practice filth hangs
about the pans of the closets. Consequently, if any putrefying
action went on in the pipes, decomposing matter or injurious
gases might be liable to pass into the houses, if not in spite
of the vacuum in the pipes and reservoirs, at all events when
the vacuum is not in operation.
This method of removal of excreta necessarily requires
a system of sewers, in addition, to carry off the water from
baths, washing, kitchens, &c., and rain water.
It follows from these observations that except in cases where
some special conditions prevail, it will be more convenient in
towns, that the drains, which must be provided to remove
waste water and water fouled in daily use, should also be
employed to carry off the excreta and similar refuse which
requires immediate removal from the houses.
CHAPTER XVII.
DRAINS IN A DWELLING.
The removal from a dwelling of the water which has been
polluted in the processes of daily life is a separate question
from that as to how the refuse water is to be dealt with after
removal.
The chief objects of a perfect system of house drainage
are —
1. The immediate and complete removal from the house of
all foul and effete matter directly it is produced.
2. The prevention of any back current of foul air into the
house through the pipes or drains which are used for removing
the foul matter.
The first object, viz. removal of foul matter, can commonly
be best attained by the water-closet system when carried out
in its integrity, though in certain cases a system of earth, or
other form of dry closet, may be preferable. Cesspools in a
house do not fulfil this condition of immediate removal. They
serve for the retention of excremental and other matters,
and they are inadmissible where complete removal can be
effected. Where this is not possible, and cesspools must be
had recourse to, they must be carefully designed ; they must
be placed outside, and as far removed from the immediate
neighbourhood of the dwelling as circumstances will allow.
/
Drains in a Dwelling.
It has been the practice to cany
the overflow from cisterns into the
soil-pipe from the water-closet, with
'ater-trap between. ,
lorecver, it has also been largely
practice to carry the soil-pipe into
rain, and to connect that drain
[i a sewer; providing as the only
ins for preventing the gases from
sewer from entering into the house,
t a 3ap at the end of the drain at
:ommunication with the sewer, and
:t,trapsbelow the water-closet basin.
Such an arrangement is extremely
igerous. The flaps, even if they
ed well, would allow sewer-gas to
s into the house drain each time
t a flap was opened by the pressure
the water in its effort to pass from
house drain into the sewer.
!n inspecting sewers it will be fre-
;ntly noticed that a bit of straw or
)er will lodge under the flap, and
;p it slightly opened.
?ewer gas, thus entering, would pass
the drain to the soil-pipe, where,
each time that a Volume
of water was thrown
JOT^-. down, some of it would
a '■!.: necessarily be forced
through one or other
KA^^___of the traps, to make
^ way for the inflowing
water.
Fig- 50-
Drains in a Dwelling. 241
Eut independently of this, the capacity of water to absorb
sewer-gas is very great, consequently the water in the trap
would absorb this gas. When the water became warm from
increase of temperature it would give out the gas into the
house ; when it cooled down at night it would again absorb
more gas from the soil-pipe : and frequent change of tem-
perature would cause it to give out and re-absorb the gas
continually.
Hence if the trapped waste-pipe from a cistern is passed
into the soil pipe it will allow sewer-gas to pass through, and
be absorbed by the water in the cistern ; but many cisterns
have a waste-pipe directly communicating with the soil-pipe,
without any trap between.
Thus a water-trap without other precautions is but a frail
protection against this very insidious and dangerous enemy,
sewer-gas, especially in a concentrated condition.
There is, moreover, another element of danger in the
water-trap. When a body of water is thrown down a closed
soil-pipe it tends to draw in air, and is followed by the water
from all the traps communicating with the soil-pipe, and thus
the trap is frequently left without water.
To prevent these evils the followii^ points should be
attended to in house drainage : —
I. General arrangement and position of drains.
The first object to be attained in house drainage is
to prevent the sewer-gas from pass-
ing from the main sewer into the
house drains. The flap will not pre-
vent it, and therefore a water-trap
should be interposed. This water-
trap should have as little surface as
possible. ^^-S'-
In large houses the break of connection with the sewer
may be by a disconnecting manhole (see Fig. 51).
In small houses it may be arranged to take a branch
242 Drains in a Dwelling.
pipe off the house drain, on the house side of the syphon,
and to bring this branch up to the surface of the ground,
as shewn in Fig. 50; in cases where this branch can be
laid at an angle of about 45^ it will not only act as a
ventilator, but the syphon can be cleaned from it in case of
stoppage.
The house drain if closely sealed by water traps will become
a reservoir for the sewer-gas which may pass through this
water-trap. It is therefore necessary in the next place to
oxidise or aerate this gas. To do this we must ensure that
a current of air shall be continually passing through the
drains ; both an inlet and an outlet for fresh air must be
provided in the portions of the house drain which are cut off
from the main sewer, for without an inlet and outlet there
can be no efficient ventilation. This outlet and inlet can
be obtained in the following manner. In the first place, an
outlet may be formed by prolonging the soil-pipe at its full
diameter and with an open top to above the roof, in a
position away from windows, skylights, or chimneys ; and
every branch pipe connected with a soil-pipe should be
similarly carried up, and be left open at the top for ventila-
tion. And secondly, an inlet may be obtained by an opening
into the house drain, on the dwelling side of and close to
the trap, by means of the disconnecting manhole or branch
pipe before mentioned, or where necessary by carrying up
the inlet by means of a ventilating pipe to above the roof.
The inlet should be equal in area to the drain-pipe, and
not in any case less than four inches in diameter. In an
open situation, and at a distance from a house, the pipe
might be dispensed with. If the opening is low down
and near openings into the house, it may be covered by
a charcoal air-filter of an area at least six times that of the
pipe, which should be carefully protected from wet, so that
its action may not be impeded. This is advisable to prevent
smell in case there should be deposit in the pipes, and in
Drains in a Dwelling. 243
case circumstances should arise to reverse the ventilation and
convert the inlet temporarily into an outlet, or vice versA.
Much of the value of these arrangements is lost, if the
house drains be laid so as to allow of deposit ; because if
deposits occur in the drains or traps, they will putrefy and
develop sewer-gas. But if the house drain and soil-pipe
have a sufficient uniform fall to remove the refuse at once,
and if they be well ventilated — and the more the openings
the better — ^very little smell will arise. Indeed soil-pipes and
drains cannot be too open or too much ventilated, provided
always that they are cut off by a water-trap from the main
sewer, which should always be ventilated also.
Flues in walls should not be used for sewer or drain venti-
lation ; the sewer-gas would be liable to permeate the wall
and pass into the house. All pipes or openings for ventilation
should be external. Ventilating pipes should be carried
upwards without angles or horizontal lengths, and with air-
tight joints. The, upper end should not be near windows or
ventilating openings, and in confined spaces should be carried
above the level of the ridge of the roof.
The best position for a soil-pipe is outside the house;
because any escape of sewer-gas resulting from defective joints,
corrosion, or otherwise would take place in the open air.
In very cold climates, or very exposed localities, pipes so
placed would require protection from the frost.
The mean temperature of the internal air in town sewers in
this country from a year's experiments was found to be about
I2&° higher than the external air in winter, and 3° cooler than
the outer air in summer. The temperature of sewage is always
above freezing point, and in this country danger from frost
might easily be guarded against.
It is unnecessary for waste-pipes from baths, lavatories, or
sinks (except slop sinks for urine, or water-closet sinks, such
as are used in hospitals) to pass direct into the drain.
Similarly, it is unnecessary and undesirable for waste-pipes
R 2,
244 Drains in a Dwelling.
from cisterns or rain-water tanks to communicate with drains.
Ih a well-arranged set of cisterns in a house, the overflow
from the upper cistern will fill the lower ones consecutively,
so that one waste from the lower cistern would suffice, and
this one should deliver into the open air. Moreover, to prevent
the possibility of the drinking water becoming polluted by
sewer-gas, which might find its way up the pipe which supplies
water to the closet-pan, each water-closet should have its own
special cistern, supplied by a ball-cock from the principal
cistern, and it should not be possible to draw water from any
cistern supplying a water-closet for any other purpose than
the supply of such water-closet.
It should therefore be an absolute rule that no overflow or
waste-pipe from any cistern or rain-water tank^ or from any
sink other than a slop-sink for urine, or slop-sinks for hospital
use, or from any bath or lavatory, or safe of a bath^ or of a
water-closet, or of a lavatory, should pass directly to any
drain, soil-pipe, or trap of a water-closet ; but every such pipe
should pass through the wall to the outside of the house and
discharge near or over trapped gullies with an end open to
the air, or deliver into a pipe which so passes and discharges.
But all waste-pipes should be properly trapped close to the
sink or lavatory or bath, because any pipe through which
fouled water passes at intervals will have its interior coated
with deposit, which will occasion a smell. This smell will
be removed by fresh air, therefore a current of air should be
maintained in all waste-pipes which are open at the bottom,
by means of an opening at the upper part as far away from
windows as can be conveniently managed. Care must be
taken to protect waste-pipes against frost.
Sinks and water-closets should be placed against external
walls, so that the pipes conveying refuse water or soil may
be more immediately passed outside the main wall, and so
that the rooms or closets so appropriated may have windows
opening directly to the air.
Drains in a Dwelling. 545
Water-closets or sinks situated within houses which have
no means of direct daylight and external air-ventilation, are
liable to become nuisances, and may be injurious to health ;
and if such sinks and water-closets cannot be ventilated in an
efficient manner they had better be removed.
%, Constructional requirements in laying house drains.
Every drain should be laid in a straight line with proper
falls and true gradients. All drains and soil-pipes should be
round and not angular. Round pipes are more self-cleansing
than angular pipes, and the circumference being smaller in
proportion to the area, they cause less friction in the passage
of the fluid.
Drain-pipes as distinguished from soil-pipes and other
down pipes, are generally (i) o£ glazed stone-ware, with
asphalte joints for inside work and cement joints for outside
work ; (a) of concrete cemented inside and with cement joints ;
or (3) of cast iron pipes coated inside with tar, with lead
water-tight joints. Lead joints can only be made in a strong
iron pipe; and the use of these joints is to some extent a
guarantee of soundness, but every iron pipe should be care-
fully tested by water pressure to see that there are no holes
or flaws.
The use of cast iron for house drains, if the Cast iron is
solid, sound, and free from porosity, will prevent leakage and
subsoil tainting beneath the house, and will be as cheap as
earthenware pipes in many cases.
In laying pipes in the ground, sufficient space should be cut
out in the ground at the joints to allow of a good joint being
made, and examined before being closed in ; to ensure
accuracy in laying, the pipes for house drains should always
be bedded in concrete. No right-angled junction should be
allowed, except in the case of a drain discharging into a
vertical shaft. It is advisable to construct access channels
with manholes at every change of direction, to admit of
examination of the drain.
246 Drains in a Dtvelling.
No drain should pass through and under a dwelling-house,
except where absolutely necessary. When it must so pass, it
should be laid in a straight line under the house, between
disconnecting manholes placed outside the house, arranged
for cleansing and examination ; the portion of the drain
which is under the house should be laid in an air drain,
so constructed as to be as impermeable as possible, open
to the air at each end, and allowing access to the drain-
pipes when necessary. Where possible, all connections with
drains should be made outside a house.
In laying the drain-pipes proper junctions must be pro-
vided in all drains for sink and water-closet drainage, and
for drain ventilation; because communications with drains
without proper junctions lead to deposit and leakage.
For an ordinary house a 4-inch drain-pipe is ample — a 6-
inch pipe would be required for a large hotel — a 9-inch pipe
would suffice for a very large building. To ensure freedom
from deposit pipes for moderate sized houses should never be
larger than six inches.
A fall of I in 40 is a good fall for a 4-inch drain,
„ I in 60 „ „ 6
I in 80 „ „ 9
If from insufficient fall or other causes the drain cannot
be kept clear of deposit without flushing, special flushing
arrangements must be provided. Leaving taps open, and
propping the handles of water-closets, will not flush drains, but
will only waste water. A large flush of water is required
for flushing drains. Where water is plentiful, a discharge
direct from a large cistern provided for the purpose may be
obtained. Where water is limited, the drains may be flushed
by introducing small paddles in grooves formed at the access
or junction chambers, and suddenly releasing the pent-up
water ; or where the flow of sewage is small, a tumbler flush-
ing box or Field's self-acting flush-tank may be used.
Mr. Roger Field's flush-tank is designed for flushing
Drains in a Dwelling,
247
Fig. 52.
house drains, but may of course also be used for flushing
sewers. The syphon is so constructed as to be put in action
by a very small constant flow of water. This is efiected by
making the discharging limb of the syphon and its connection
with the bend of the syphon in such a way that when a small
quantity of water flows over the bend, it falls clear of the
sides, instead of running down along the sides of the dis-
charging limb.
By this arrangement, the water as it
drops carries away the air in the dis-
charging limb, and thereby starts the
syphon. The longer limb of the syphon
must be dipped into water below the
tank. A convenient arrangement for this
purpose is an annular form of syphon, as
shown in the drawing. By this means
a large syphon can be put in action by
a very small flow of water, so that a
large flushing tank may be fed, for
instance, by the constant flow from a
small water-tap which would take a day
or two to fill it, and yet the tank will
discharge itself automatically as soon as
it is full.
The syphon is capable of being easily
taken to pieces in case of any stoppage
occurring. The outer case can be
readily lifted off", and as readily replaced
for the purpose of examining or cleansing
the syphon.
Rain-water pipes should deliver into
an open channel or over a gully, or in
some other way so as to have the dis-
charging end open to the air. In special cases they may be
connected with the drain so as to be used as ventilating
Fig. 53.
248 Drains in a Dwelling.
pipes, provided their upper extremities are situated at such
a distance from windows, openings, or projecting eaves, as
to ensure that there is no danger of escape of foul air into the
interior of the house from the pipes. When so used the joints
should be air-tight.
All inlets to drains should be properly trapped, except
where left open for ventilation of the drains.
The gullies to receive discharge from waste-pipes or rain-
water pipes, surface drainage or otherwise, should be trapped
(see Fig. 54, $5) : they should be placed at a distance of a
yard at least from windows. The waste-pipe from a sink
may discharge under a grating for appearance sake.
Fig. 54- Fig. 55-
The surface of water exposed in a trapped gully should be
as small as possible, compatible with facilities of cleansing, so
as to limit the surface for evaporation. The gully at which
the waste-pipe from a scullery sink discharges should be pro-
vided with a grease-trap outside the house ; otherwise grease
may choke the drains.
Gullies should not be placed inside a house, in cellars, base-
ments, or otherwise, unless absolutely necessary. Where such
gully cannot be avoided, it should be properly trapped, and
the outlet pipes should not pass directly to any drain or
sewer, but should be disconnected therefrom by passing
through the wall to the outside of the house, and there de-
livering with an end open to the air over a suitable trap or in
Drains in a Dwelling. 249
a disconnecting manhole (Fig. 56). Where the basement is so
deep that this could not be arranged, it would be advisable to
run the drain to a small brick and cemented well-hole to be
pumped out daily, or when occasion might require, so as to
avoid direct communication with a drain.
When from the damp-
ness of a site it is neces-
sary to lay subsoil or
land drains, and to dis-
charge the water into a
sewage drain, the sub-
soil or land drain should
not pass directly to the
sewage drain or sewer,
but should deliver into
a disconnecting man-
hole, as in Fig. 51, 56.
■ All inlets to the
drains and all openings
for ventilation should be
efficiently protected by
gratings, to prevent the
introduction of improper
substances. When not
so protected the gully
should be arranged (Fig. y\%, s6.
51) so that stones, sand,
or other heavy matters falling in will drop to the bottom clear
of the trap and entrance to the drain ; and the gratings
should be moveable, to allow of such heavy matters being
easily removed from the bottom of the gully, and they should
be cleaned out periodically.
Gratings to inlets, or openings used for ventilation or dis-
connection, should have a free air-space at least equal in area
to that of the drain-pipe or gully at the place.
250 Drains in a Dwelling.
Gratings should be made of a form to allow the water to
pass freely, and to prevent dirt from lodging and choking
the passage for the water. Circular holes are least adapted
of any form for allowing water to pass.
3. Soil and waste pipes.
Soil pipes carry away the discharge from water-closets and
from slop-sinks.
A 4-inch diameter soil-pipe is sufficient for ordinary sized
houses ; if many closets are on the same pipe then a 4|-inch
or 5-inch may be necessary, very rarely a larger size. Solid
drawn lead pipes are preferable. 6 lbs. lead is the least
thickness admissible. 7 or 8 lbs. lead, and more, with the
larger pipes, should be used in all cases where hot water is
occasionally thrown down, being better calculated to resist
the alternate expansion and contraction.
Iron pipes are sometimes used, but the making of a perfect
joint is more certain with lead than with iron ; and cast iron,
if used, must be sound, and free from porosity. Joints in iron
pipes should be made with lead. Cement joints cannot be
relied on, either for lead or iron pipes, as they may crack.
The down pipe, whether lead or iron, must be properly sup-
ported at intervals, so that its weight or the jar of the flow of
water shall not tend to move it and open the joints, either
at the junction with the closets or at the bottom, and thus
allow of a leak of sewer-gas.
Lead soil-pipes are usually supported by blocks at every ten
feet, but intermediate supports by means of a flange or a tack
soldered to the pipes are desirable. Soil or down pipes placed
inside a house should be placed in a space built in the wall, of
sufficient size to allow of the joints being well made and
examined. If placed in chases cut in the wall, the sides of
the chase should be carefully cemented and smooth. Casings
made to open should be provided to the chases. But it is far
preferable that where possible the soil-pipes should be entirely
outside the house ; so that if a leak should occur, it will not
Drains in a Dwelling. ^ 251
do much harm ; because there is always danger of concealed
lead pipes being injured by nails being driven into them
inadvertently.
The connection with the drain should be outside, because
the junction of the vertical soil-pipe with the house drain is
a place at which there is always risk of cracks, which would
allow of the leakage of sewer-gas. On this account it is
advisable when a lead or an iron soil-pipe must terminate in
an earthenware drain-pipe inside a house that the bottom of
the soil-pipe should discharge into a trap in the earthenware
pipe. In such a case the horizontal drain and the soil-pipe
should each have independent adequate ventilation by an
inlet and outlet for air.
The waste from a cistern should be of a size capable of
emptying the cistern very rapidly from its lowest point, so
that the cistern may be easily cleaned. Cisterns should be
throughly cleaned out at least once a month. The water
from the cistern should not discharge directly over or into a
gully, for fear the trap should be dry and foul air pass up the
waste into the cistern.
Waste-pipes from baths, as well as the valves, should be at
least 2 inches diameter, and from basins at least i^ inches
diameter for comfort. Lead waste-pipes carrying away hot
water, should be of at least 8 lbs. lead. Where branch wastes
ce^mmifeate with a main waste-pipe, bends in the branch
waste are desiraBleTo allow for the expansion and contraction
of the wastes.
4. Fittings for water-closets.
Many kinds of water-closet apparatus and of so-called
' traps ' have a tendency to retain foul matter in the house,
and therefore in reality partake more or less of the nature of
small cesspools ; and nuisances are frequently attributed to
the ingress of * sewer-gas' which have nothing whatever to do
with the sewers, but arise from foul air generated in the house
drains and internal fittings.
252 Drains in a Dwelling.
The ordinary form is a basin with a hole below, which is
sealed by a moveable lower basin, which holds the water. A
lever movement is required to. drop the second basin, so that
its contents may pass into the drain ; but, in order to prevent
the sewer-gas from passing through the hole in the first basin
at the moment of discharge of the contents, and up into the
closet, and also in order to prevent the sewer-gas from pass-
ing, as it would do continuously, round the lever apparatus
into the closet, the contents of the moveable or second basin
are dropped into a receptacle with a D trap.
This trap is out of sight, and it is necessarily rather large,
and from its shape it is liable to accumulate much foul putres-
cent matter. To remedy this hundreds of forms of water-
closet pans have been introduced, of more or less merit.
In the selection of a pan, the object to be attained is to
take that form in which all the parts of the trap can be easily
examined and cleaned, in which both the pan and the trap
will be washed clean by the water at each discharge, and in
which the lever movement of the handle will not allow of the
passage of sewer-gas.
The trap is, however, useless if any escape of gas can take
place at its junction with the waste-pipe ; consequently the
trap should always form a portion of the soil or waste-pipe,
instead of a part of the fitting, and the water-closet or sink
should be capable of being moved without disturbing the trap.
Lead is the best material in a house for traps and waste-pipes,
because it is smooth, durable, free from corrosion, and joints
can be made easily and safely in lead. For outside work
stone-ware may be used. The best form of lead trap is a
smooth cast lead trap without corners. When such a volume
of water is thrown into a trap as completely to fill it, the trap
will act like a syphon and empty the pipe, leaving the trap
without water ; consequently it is desirable to have a small
ventilating pipe at the bend beyond the trap carried into the
main ventilating pipe or into the open air, to prevent the
Drains in a Dwelling. 253
syphoning action. Lead traps through which hot water passes
should be of 8 lbs. lead. No trap should be of less than 6 lbs.
lead.
The depth of dip of a trap varies from half an inch to as
much as 3^ inches. It should depend on the frequency of use.
When rarely used more depth of water is required, to prevent
the trap failing from evaporation. Openings for cleaning
traps should be below the water-level of the trap, then they
show by a leak if they are not tight.
5. Cesspits.
The arrangements described have special reference to the
case of sewers ; but in certain cases, such as private houses, or
small detached barracks, it is convenient, and indeed often
necessary to provide a cesspit, to receive and retain the
refuse for a certain time.
The old form of cesspit was to dig a hole in the ground ;
if porous ground, so much the better ; and to pour into this
the whole foul refuse of the house or barracks, until its over-
flow compelled its cleaning out. Numerous cesspits of this
sort used to exist in barracks, which the porous soil had so
m
favoured that there had been no necessity to empty them out
for many years. These cesspits consequently saturated the
soil and polluted the adjacent wells.
From what has been said of the movement of ground air, it
is apparent how dangerous this mode of dealing with refuse
must be, especially if the cesspit is near the house. Of
course the risk of danger to a house from this pollution of
ground air from the cesspit will increase with the depth of the
cesspit. But in addition to the risk of pollution of the ground
air, there is the risk of pollution of water in adjacent wells.
If it is necessary at any place to turn the refuse into cess-
pits, the cesspits should be made impervious by puddling
outside, and lining with brickwork in cement ; they should be
as small in size as circumstances allow, so as to necessitate
frequent cleansing.
254 Drains in a Dwelling.
It is essential that the gases geaerated in the cesspit
should not pass into the house drain.
The cesspit must be covered, but if necessarily near a
dwelling, it should have ventilation through a lai^e charcoal
filtering screen, carefully protected from wet ; If away from
dwellings, large openings protected from rain would suffice ;
and there should be a water-trap between the cesspit and
the house ; and between this trap and the house, the ventila-
tion of the house drains should be arranged on the principles
already described, so as to ensure that any gases which pass
the trap may have an opportunity of being diluted with fresh
air.
When cesspits, or sewage filters have to be provided for
barracks, as frequently occurs in the new Depot Brigade
Fig. 57. VentiEator for Cesspool.
Barracks, they should invariably be outside the barrack en-
closure, and removed from the barracks as far as the ground
in possession of the Government will allow.
In these suggestions it is assumed that the sewers or cess-
pits from which the house drain is cut off, are themselves ade-
quately ventilated, for otherwise the precautions suggested
would be much less effective.
6, Examination of drains.
It will be seen from these few remarks that in the question
of house drainage safety depends quite as much on the work-
man who executes the work as on the architect or engineer
Drains in a Dwelling. 255
who designs it ; and this part of the subject would not be
complete without a few observations on the examination of
house drains.
In examining a drain the main drain should be opened at
the point where it leaves the house, and by pouring water
down the various closets, sinks, bell-traps, and rain-water
pipes, the various pipes may be traced, and an opinion formed
as to the state of the drains. The velocity of the water flow-
ing in the drain may be ascertained by pouring water down
at any point, and accurately noting the time it takes to reach
the opening. After examining the basement, every closet,
sink, bath, &c., should be examined in detail. To do this it
is necessary to have the wooden casings, seats of closets, Sc,
removed, to trace how each closet, sink, bath, &c., is supplied
with water, how the soil-pipes from the closets, and the waste-
pipes from sinks, baths, overflows of cisterns, waste to safes,
&c., discharge. It can be determined whether the drains are
trapped off* from the main sewer by ascertaining if there is
any draught from the bell-traps in the sinks.
To test the drains, the fumes of ether or of sulphur may be
used. If ether is poured down a soil-pipe the fumes will be
perceptible in the house at any leaks in the soil-pipe or
failures in the traps. Sulphur fumes may be applied by
putting into an opening made in the lowest part of the drain
an iron pan containing a few live coals, and throwing one or
more handfuls of sulphur upon the coals, and closing up the
opening to the drain with clay or otherwise. The fumes will
soon be very perceptible at any leaks or rat-holes in the soil-
pipe, drains, or traps.
CHAPTER XVIII.
CONDITIONS TO BE OBSERVED IN MAIN SEWERAGE
WORKS.
Whatever may be the system adopted for the removal of
the excreta, there will always be a large amount of liquid
refuse to be dealt with which is liable to putrefy, and conse-
quently; in providing for the removal of this, it is generally
more economical to arrange at the same time for removing
the excreta, than to institute a separate service for each.
In the removal of the foul water, the question is often
mooted of providing for the water used in households only,
and making a separate service for rainfall.
This question is one which has obtained considerable
importance from the theoretical views which have sometimes
been permitted to decide it.
A strict rule cannot be laid down. In the case of a detached
house or of a barrack, or of a small collection of houses, the
conditions are very different from those in large or even
moderate sized towns.
In the case of detached houses and barracks, it is frequently
found advisable to save the water which falls on roofs, and to
use it for washing and other purposes requiring soft water.
But when, as in a large town, the ground is closely occupied
by houses, the rain-water, as it falls, is fouled by soot ; and it
Conditions to be observed in Main Sewerage Works. 257
moreover takes up many other impurities from the atmo*
sphere, and is unfit for domestic use.
In a town area, whilst the soot and the impurities of the
atmosphere which the rain-water takes up in falling frequently
render it unfit for domestic purposes, that which falls on
streets and yards is made quite foul by the large quantities
of horse-dung and other impurities which are the chief consti*
tuents of the street dust in towns.
Experiments made by Professor Way some years ago on
the rain-water which passed into sewers, showed that whilst a
small part of the solid matter from paved streets consisted of
granite, "the bulk was horse-dung ; and he showed that the
value as manure of street water taken in rainy weather on its
way to the sewers was as great, or even greater, than the
ordinary contents of the dry weather sewage.
It is on these grounds necessary to provide in the drainage
of a large town, as far as possible, for the removal of the foul
street and yard water, as well as the house sewage proper.
If provision were made for the very large amount of rainfall
which may be expected to occur exceptionally and at rare
intervals, other elements of inconvenience and even danger to
health would be introduced. For instance, the small amount
of the dry weather flow of sewage would necessarily only form
a trickling and stagnating stream in a sewer calculated to re-
move the maximum volume of rainfall, and this dry weather flow
would be liable to create deposits. A large sewer, in which
deposits can occur, would forni a great reservoir for sewer-gas.
Where provision is made for rainfall, the nature of the
area which has to be drained must regulate the proportion
of rainfall to be removed. For instance, in a town area,
closely built over, the rain-water will run off rapidly into
the drain ; in a suburban area, that which falls on garden
ground will pass off more slowly. The rain-water which
passes from streets and courts into a sewer during a storm
immediately succeeding a dry season, is generally richer in
S
258 Conditions to be observed in
manurial value than that which passes in after the rain has
lasted some time.
But in any town or district sewered effectively, in which
the admission of surface water is limited, and in which the
subsoil waters are excluded from the sewers, the volume of
sewage will be reduced, and be thus more easily dealt with,
either by pumping or by gravitating to land for irrigation.
The excess of rainfall not provided for in sewers must be
carried off by carefully formed surface drains ; or else by
storm overflow channels formed in the sewers to pass the
water into natural watercourses : to effect this object many
ingenious devices have been designed.
The flow of water from a drainage area during continued
heavy rain, as in a wet season, or during a thunderstorm, may
swell the rivers and natural .streams so as to swamp and
water-log the lower parts of the sewers. When the outfall is in
a tidal estuary or in the sea, tides are liable to backwater the
outlet-sewers. Some tidal rivers in England rise vertically in
flood as much as 20 feet. In some of these cases pumping is
resorted to ; in other cases the sewage is retained in tanks, or
in tank-sewers, until the ebbing of the tide, and no absolute
rule can be given when one or the other mode shall or shall
not be adopted. Where an outlet sewer is liable to be back-
watered, it may sometimes be advisable to keep the invert up
as much as possible, even at the expense of the gradient, and
to depend on flushing.
The question as to whether this plan should be adopted, or
whether on the other hand the invert should be kept down,
although liable to be backwatered daily, will depend upon
whether a sufficient velocity of flow can be obtained during
the period of maximum discharge to remove any silt which
may have have been deposited during the stagnation arising
from the backwater.
The velocity of flow of water which will move materials is
regulated by the following considerations : — (i) For objects of
Main Sewerage Works, 259
the same character, the velocity required to start them in-
creases with the mass of the object ; {%) for different objects,
the velocity required increases with the specific gravity ;
(3) according as the object assumes a form approaching a
sphere, the less velocity it takes to move it ; whereas a flat
object, like slate, requires a considerable current before it
becomes disturbed from its position ; (4) the object moves at
a less rate than the current, but when the velocity of current
increases after an object is in motion, the velocity of such
object increases in a progressive ratio.
A velocity which will start an object will (when constantly
maintained, and no accidental circumstance occurs to prevent
it) never allow such object to deposit in the stream.
A velocity of from 2 feet to 2 feet 6 inches per second with
a continuous flow will remove all objects of the nature of those
likely to be found in sewers ; but if the flow is intermittent, or
if a part of the sewer remains occasionally stagnant, a velocity
of 3 feet would be advisable during a portion at least of the
period of maximum flow.
Sewage should not be allowed to acquire a velocity of
more than four feet per second. Six feet per second will
move grit and other solids along the sewer invert, with a
cutting action rapidly destructive of the material of the sewer.
The sewage of a town or village will consist of waste-water
and excreta from the houses, and the volume, in round figures,
may range from 100 to 2^0 gallons per day from each house.
This flow of sewage is not uniform throughout the day. It
varies with different places, according to the habits of the
people. In London, 46 per cent, of the daily dry weather
flow reaches the outfalls between 11 a.m. and 8 p.m., whilst
only 21 per cent, flows off between % a.m. and 9 a.m. The
largest flow per hour amounts to 6 per cent., and the smallest
to v6 per cent, of the whole daily dry weather discharge. The
volume of maximum flow regulates the size of the sewer, so
far as sewage is concerned.
S %
26o Conditions to be observed in
In addition to this, the provision for rainfall has been
assumed in London at \ of an inch of rainfall to be carried off
in 24 hours from the urban districts, and | of an inch in Z4.
hours for the suburban districts.
As all rainfall cannot be excluded from the sewers, it has
been suggested to provide for a total amount of not less than
1000 gallons from each house ; that is to say, for a town of
1000 houses (5500 population) the sewers should have a deli-
vering capacity of about 1,000,000 gallons. An outlet-sewer of
% feet diameter, laid with a fall of 5 feet per mile, will deliver
upwards of 2,000,000 gallons, flowing a little more than half
full ; and as provision should be made for increase of popula-
tion, a sewer of 2 feet diameter may be provided for each 5500
persons, where no better fall than i in 1000 can be obtained.
Lesser diameters will answer where there are greater falls.
A comparatively long line of outlet-sewer may be necessary
to intercept and take the sewage of several lines of sewers
to some common outlet, where there are sewage tanks, or
* sewage-farms ' ; this outlet may, however, be confined to, say,
three times the ordinary flow of sewage, if storm-water over-
flows can be provided ; because it would not as a rule be
desirable to construct the intercepting sewer of sufllicient
capacity to remove storm-water, .as neither sewage-tanks
nor sewage-farms can deal satisfactorily with such excessive
volumes of water. In some cases it may be necessary to
provide a storm-water sewage-tank ; for this purpose an area
of low-lying land may be deep drained and embanked, and
the excess of sewage during rain be discharged on to it and
left to filter away in the intervals. Such an area would-be
a rough sewage-filter, to be used during wet seasons. A
portion of land on the margin of a watercourse may, in some
cases, be embanked above flood-level for this purpose.
In laying out the sewerage of a town, it is of importance
that the water from the highest levels should be carried off*
independently of the lower levels, when it can be done.
Main. Sewerage Works. 261
Gibraltar afforded a striking instance of this (Fig. 58). The
town is at the foot of the rock — part is situated on the steep
side of the rock, and part on a flat piece of land, which is
separated from the sea by the fortifications.
The sewers were carried down the steep streets, which ran
from the upper part of the town, across the flat portion of the
town, and through the line wall into the sea. One of the main
sewers commenced at a height of about 138 feet above h^h
water mark, and reached the sea-level after a course of about
1000 feet.
Another commenced at a height of 264 feet, and descended
to the sea-level after a course of about 1500 feet, 500 feet of
the lower end being nearly horizontal. A third had a lall of
Fig. 53. Former Sewers at Gibraltar,
264 feet in 2200 feet. A fourth discharged its water into a
nearly horizontal main, after a fall of 232 feet in 1550 feet.
Therefore the rainfall on the surface of the town, and on
the roofs of the houses, together with the deluge of surface
water which descended from the highly inclined slopes of the
rock above, ran with extreme rapidity from all the higher
levels into the lower and flatter districts, where it used to
burst the sewers, saturate the subsoil, and interfere with the
eflicient drainage of all the lower parts of the town.
The rapid current down the steep part became a slow
stream in the flat portion, deposited a large sediment, and
in dry weather became a source of intolerable nuisance. This
262 Condi ttofis to be observed in
has now been remedied by an intercepting sewer, which
carries the water from the upper part of the town to the sea,
independently of the lower levels.
Sewers liable to be affected by the rise of tides or land
floods, as on the sea-shore or on a river, must be so arranged
that any backing of the sewage shall not injuriously affect the
sewers and drains within the town.
The lower districts of London used to suffer from periodical
flooding in consequence of the water from the high districts
coming down upon the lower districts ; with the aggravation
that the sewers delivered through the low level districts only
at low water.
The intercepting sewers now laid down in London, carry
off the water which falls on the upper districts by gravitation,
whilst the water carried off by the sewers in the lower levels
has to be pumped.
The lower portion of any system of sewers below the level
of high water of the sea or the land floods of an inland river,
must be cut off from the upper portions, which should have
an entirely independent outlet, and both systems must be so
abundantly ventilated that any sewage gases which may be
formed may pass out at points specially provided for the
purpose, and not through the drains and into the houses.
The intercepting system is especially needful in towns
where the levels vary much, because a sewer which is carried
down a steep hill becomes a chimney up which the sewer-gas
flows, and may pass through the drains into the houses at the
upper part. Consequently, whdh a sewer is necessarily placed
in such a position, the highest part should be kept open, and
numerous openings should be provided in its course to allow
of its complete aeration.
Means for full and permanent ventilation of town sewers
and house drains are required to prevent stagnation or con-
centration of sewage gases within sewers and drains. Ventila-
tion requires both inlets and outlets : these will be adequately
Main Sewerage Works. 263
aflforded by making numerous openings from the sewers to
the external air, the object being to cause unceasing motion
and interchange betwixt the outer air and the inner sewer air,
which will bring about and maintain extreme dilution and
dispersion of any sewage gas so soon as generated.
It has been found by experiment that in unventilated
sewers the concentrated gas becomes deadly, whilst in fully
ventilated sewers with continued flow without deposit, the
sewer air is purer than that of stables, or even than that in
a public room when fully occupied.
Ordinary main sewer ventilation should be provided for all
sewers, at intervals not greater than 100 yards ; that is to say,
not fewer than 18 fixed openings for ventilation should exist
on each mile of main sewer.
If sewer air' at any sewer ventilator, or at any other point,
should be offensive, additional means for prevention of deposit
and for ventilation on this sewer are required, and should, as
soon as possible, be supplied.
Although in properly constructed sewers the ventilation
should prevent any smell, in old sewers of defective construction
charcoal filters for the ventilations may sometimes be advisable.
Where charcoal is used in sewer ventilation it must be under-
stood that it retards motion, and provision should be made to
meet this. Charcoal trays, or boxes, for sewer ventilation,
should never have less than 1000 square inches of surface
exposed for the passage of sewage gas to each 50 square
inches of free opening to the outer air. The meshes of a
charcoal tray may be about Jth of an inch. The charcoal
(wood) may be about the size of coffee beans, clean sifted, and
placed carefully in a layer of ^ or 3 inches. It should be
carefully protected from wet. The vibration of the traffic in
a street is said to consolidate it so as to check its action.
Charcoal in a dry state acts the best, but its disinfecting
property is only diminished by damp — it is not entirely
destroyed. The charcoal may require, in some places, to be
264 Conditions to be observed in
renewed at intervals of six months. It should only be looked
on as a makeshift; in ordinary cases of sewer ventilation
charcoal need not be used, as the more readily and freely
the interchange can take place from the sewer or drain to the
outer air the better will the ventilation be.
The upper, or * dead ends,' of all sewers and drains should
have means provided for full ventilation continued beyond the
junction of the last house drain.
For detached houses, villa residences, or larger establish-
ments, drains should never end at the house which has to be
drained, but should be continued beyond and above to some
higher point or ventilating shaft where means for full and
permanent vehtilation can be provided, so as effectively to
relieve the house from any chance of sewage gas contamination.
With the abundant means for ventilation suggested, the air
within the sewers will be made comparatively pure by dilution
and oxidation, and the further dilution and dispersion which
would occur when the gas passes into the open air will
generally dissipate remaining traces of taint and danger.
Manholes should have moveable covers at the surface
of the ground. There should be a side chamber for ventila-
tion, 'step irons,' to give access to the invert, and a groove
in the invert and sides to allow of a flushing board being
inserted at will for flushing purposes. The side chamber
might be arranged for a charcoal screen or filter, where
from the defective construction of the sewer this is desirable.
Details for manhole and side chamber for sewer ventilation
are given in Figs. 59, 60.
The ends of all sewers and drains at the lowest outlets must
be so protected that the wind cannot blow in and force any
sewage gases back to the streets and houses. Flap-valves, or
other contrivances, may be provided to cover and protect
outlet ends of sewers and drains, and so prevent the wind
blowing in ; or the mouth can be turned down into the
water.
Main Sewerage Works.
265
Where the flow in the sewer is uniform in quantity, or where
the minimum flow is equal to half the maximum flow, a circular
form of sewer is best if made of such a size that the depth of
water m the sewer at the time of maximum flow shall afford
Live qfR ad
^.59. Flaoattc
Fig. 60. Plan at AA.
the maximum hydraulic mean depth (i.e. the quotient afforded
by the area of section divided by the wetted perimeter) ; but
when the flow in a sewer varies very considerably at different
times of the day, the egg-shaped form of sewer is preferred as
affording better results with a small flow of sewage. Figs. 61
266 Conditions to be observed in
and 6a show the form now generally adopted. Fig. 65 shows
the section of the river at Brussels, where it is covered over,
and the intercepting sewer which runs parallel to the river.
The sewer in this case is formed with a smaller trough at the
lower part and expanded at the upper part, by which means
a higher velocity is obtained with the dry weather flow of
Fig, 63. River and Sewer Conduits at Brussels.
sewage than would otherwise prevail, and the larger area
provides for carrying off rainfall ; during the dry weather
flow a footpath is reserved on each side. When the sewer
is quite full the overflow passes to the river through side
flaps, which the pressure forces open.
Steep gradients in sewers must be modified by forming
vertical steps, or falls, to prevent the sewj^e, during heavy
rains, from acquiring such a velocity as shall not only wear
Main Sewerage Works. 267
out the invert and blow the joints, but also burst the sewers.
The steps, or falls, should be so formed as tp prevent any
accumulation of deposit. Earthenware pipe sewers, when
laid down steep gradients, should be bedded and jointed with
concrete.
Sewers should be watertight. If the water finds its way-
out of a sewer, the diminished flow causes sediment to be
deposited, and obstructions to be created, and the subsoil
round the sewer becomes polluted with sewage matter, con-
sequently in dry porous subsoils the trench cut for the sewer
should be made watertight with clay puddle.
Brick sewers should never be set dry to be grouted — they
should be set in hydraulic mortar. If sewers are to be water-
tight so as to exclude subsoil water, the bricks must be set in
Portland lime mortar, with a lining or coating of mortar
outside the sewer, and betwixt each 4i-in. course of bricks.
Wet subsoils may require special land drains. Cast iron pipes
may be used for main sewers with economy and advantage
through quick-sands, or where the strata is full of water ; also
in narrow streets where deep trenches have to be excavated.
A cast iron sewer may be two-thirds the diameter of an
earthenware pipe or a brick sewer, as the cast iron pipe
may work full and even under pressure.
Main sewers require to be provided with storm overflows in
case of heavy rains.
Sewers should not join at right angles, unless the curve and
extra fall is provided in the manhole.
Tributary sewers should deliver sewage in the direction of
the mainflow. Fig. 64.
Sewers and drains at junctions and curves should have
extra fall to compensate for friction.
Sewers of unequal sectional diameters should not join with
level inverts, but the lesser, or tributary sewer, should have
a fall into the main sewer at least equal to the difference in
the sectional diameter. If the inverts of tributary sewers are
Steiian CD
Fig. 64. Sewer-junction 3' o" X i' o" into 4' 6" x 3' o" dtowing ade entntnce.
Conditions to be observed in Main Sewerage Works. 269
not above, or, at least, are not up to the level of the ordinary
flow of sewage in the main sewer, such tributary sewers, or
drains, will be liable to be backwatered, in which case deposit
will take place in the length of submerged invert, and so the
tributary sewer, or drain, will become choked with its own silt.
Pipe drains should have the joints made with cement. In
bad soils the joints should also be bedded in concrete, a gap
being cut to receive the concrete so that the pipes may bed
evenly.
Sewer pipes of more than eighteen inches diameter are
troublesome to handle and difficult to joint, and do not
make such good work as a brick drain.
Earthenware pipes of equal diameter should not be laid as
tributaries, but a lesser pipe should be joined on to a greater.
Side openings for house drains should be provided in the
original construction of all sewers wherever it is probable they
will be required. Every effort should be made by careful
construction to prevent sewage and sewer-gas from passing
out of the sewer into the subsoil. Where subsoil drainage is
necessary in connection with sewers, either the subsoil water
should be carried off by separate drains or the mouth of the
subsoil drain should terminate in a ventilated disconnecting
manhole, whence it should pass into the sewer.
Flushing Sewers.
Flushing a sewer means accumulating water at some point
in the sewer in sufficient quantity to pass down and along
the portion of the sewer below with a rush when suddenly
liberated, in order that the water may loosen and carry away
all sediment.
In a perfect system of sewers, flushing should be unnecessary ;
but perfection in a sewer depends as much on the excellence
of workmanship as on the design ; and any imperfections lead
to deposit and its corresponding evils.
Every care should be taken to prevent heavy substances
270 Conditions to be observed in
entering the sewers by properly formed gullies to catch and
retain the material ; especially where road washings pass into
the sewers ; and it may in some exceptional cases be desirable
to form catch-tanks in the sewer. These catch-tanks should
be wider than the sewer, so as to cause a check in the flow,
and thus cause heavy materials to be deposited, and the
bottom should be below the invert of the sewer so as to retain
the materials when dropped. The materials thus dropped
should be dredged out, at intervals, as found necessary.
As a general rule, however, sewers when true in line and
gradient, and sound in construction, and provided with side-
entrances, manholes, and flushing-chambers, at proper inter-
vals, will permit of silt being flushed through to the outlet.
As it is difficult to provide a perfect system of sewers, or to
prevent foreign heavy matters passing in, it is always safe to
provide a means of flushing. In a system of sewers every
manhole may be a flushing chamber, so managed as to be
charged with water for flushing purposes. There should also
be a flushing chamber at the head of each sewer and drain,
and every flushing chamber should be permanently ventilated.
Mr. Roger Field's flush tank, with his automatic syphon
already described, affords a convenient means of periodically
flushing drains or moderate sized sewers by the flow of water
taps or from the overflow of a drinking fountain, or other
small continuous flow which is generally wasted.
It is possible to injure sewers by overflushing them.
In towns where there is a regular water supply the flushing
chambers may be filled by the flow in the drains, otherwise
it may be necessary to resort to water carts.
Springs of water, and the water from canals, reservoirs,
rivers, and streams, may occasionally be so situated as to be
easily made available for purposes of sewer-flushing.
In the London sewers the flushing is effected by flushing-
gates provided at certain points. In the Paris and Brussels
sewers a moveable flushing apparatus is provided.
Main Sewerage Works. 271
The sewer has a footpath on each side, along which a truck
is arranged to run as on a railway, as shown in Fig. 6^, The
truck is provided with a board of the exact section of the
sewer, which can be raised or lowered by a screw apparatus
fitted to the truck. When the board is lowered, the water in
Fig. 65. Moveable flushing apparatus.
the sewer is dammed back. Two small doors are provided in
the board near the bottom, and by opening these when the
sewi^e is dammed back, a strong current of water is passed
through so as to wash away any accumulation of debris. The
truck can be moved on to any spot where the action is required.
1
^^—- —
-jg; ^
1
— ^1
\
i -i
Fig. 66. Sewage syphon
IS under the Seine at Paris.
The sewers at Paris are carried under the Seine from one
bank to another by means of pipes laid in the form of an
inverted syphon. (Fig, 66.) Each pipe is about one metre in
diameter ; to clean out the pipes a wooden ball of a diameter
272 Conditions to be observed in Main Sewerage Works.
a little less than that of the tube is periodically caused to roll
through the pipe. It delays the flow, and thus accumulates
a head of water behind it, sufficient to force away any im-
pediment from the bottom of the syphon.
There cannot be any strict rule by which to ascertain the
weight of mud any special town sewage will deposit during a
day, week, month, or year, as the weather necessarily affects
the condition of road and street surfaces, and it is (for the
most part) from dirty yards and street-surfaces that sewage-
mud is derived. A wet season will, as a rule, give from any
area more mud than a dry season. The relative weight and
character of the mud will also be determined by the character
of the street-surfaces, and the weight and rapidity of the
traffic. Paved streets produce less mud than macadamised
roads, whilst good scavenging prevents an excess of mud
being washed from the street surfaces into and through the
drains and sewers.
With respect to wear of streets and roads, rapid traffic
is destructive, heavy and rapid traffic being most destructive.
A good foundation for a road or street is of the first im-
portance, because much of the mud found on pavements
has worked up from below. Consequently all street surfaces
should be laid on a bed of concrete : by this means not only
will surface mud be diminished but the road will last longer ;
a well-formed road, though more costly to make, will be more
cheaply maintained. It is also of great importance to uSe
all proper means to prevent grit and mud being washed into
drains and sewers. For this purpose all street gullies instead
of opening directly into the sewers should be provided with
catch-pits constructed to catch and retain the detritus from
the street washings.
CHAPTER XIX.
DISPOSAL OF WATER-CARRIED SEWAGE.
The Rivers Pollution Prevention Act, 1876, forbids the
pollution of rivers and streams by the admission of crude
sewage.
At first sight, the simplest mode of getting rid of sewage is
to place it in the sea.
There are, however, towns both on the sea-shore and on
tidal estuaries in which a nuisance is caused by the discharge
of crude sewage too near to roads, houses, or bathing-places.
Moreover there are many places where this method of dis-
posing of sewage is inapplicable, and it would in any case be
singularly wasteful.
There is, however, no doubt that water carriage for the
removal of excreta is the cheapest and most convenient
system, so far as the transport to a distance is itself con-
cerned. It is only when the sewage thus removed has to
be finally disposed of without creating a nuisance that the
difficulties arise.
To dispose of sewage therefore either the outlets must be
extended into the sea, and the sewage so poured iiuthat it shall
not be returned on to the shore : or else it must be pumped
inland for irrigation, or the solids must be precipitated, and the
clarified sewage disinfected, and allowed to flow into a stream
or river.
The degree of purity to be required in clarified sewage
T
274 Disposal of
before it is admitted into a river, depends to some extent on
the degree of purity of the river water into which it is to flow.
For instance, a different standard of purity might reasonably
be admitted for water turned into the Thames at Gravesend
from that required at Oxford or Reading.
The cost of irrigation or disinfecting and clarifying sewage
so as to prepare it for passing into a stream must be regarded
as expenditure of money for cleansing the town to whose
sewage it is applied.
The disposal of sewage is a question on which the Sanitary
Engineer has expended a great share of attention, without
attaining a result which all parties have been willing to accept
as a final settlement of that question. One reason of this
arises from the fact that the question of utilisation of sewage
has been mixed up with that of removal of sewage.
The desire to make a profit has, in many cases, become
paramount, and people have been unwilling to recognise that
whilst theory shows that the utilisation of sewage in ma-
nuring the land should repay the cost, in practice there are
various barriers to financial success. Moreover, the popu-
lation in different localities is living under very various
conditions. In one part of the country the population is
scattered — and plenty of land unoccupied by dwellings can
be found for sewage irrigation. In other parts the population
is so dense that there is little room for sewage farms at any
reasonable distance from towns. In some towns chemical
products have been allowed to find their way into sewers, and
this has rendered the sewage unfit to apply to land.
The inventors of many of the systems for clarifying sewage-
water have generally advocated their projects on the ground
that profit will be derived from the manure which is to be
extracted from the sewage. If there had been no idea of profit,
the number of inventors would have been more limited, and
the subject would have received less consideration ; and, there-
fore, looking at it from this point of view, it has been
Water-carried Sewage. 275
advantaigeous for science that the idea of profit has so largely
prevailed.
On the other hand, the various corporations stayed their
hands for many years in providing drainage and water supply,
in order to wait for the discovery of this modern philosopher's
stone, and thus much sickness, death, and misery have continued
in the country, which more energetic measures would have
prevented.
It is no doubt true that sewage contains matter of enor-
mous value. The value of the manurial constituents of the
sewage of London was estimated by Dr. Hofmann in 1857 at
nearly ;^i,5oo,ooo per annum ; but he added : — * An enquiry
into the nature of the valuable matter carried off in our
sewers, an attentive examination of the chemical properties
of the constituents, together with the consideration of the
extraordinary and constantly-increasing degree of dilution in
which they exist, cannot fail to impress the chemist, on purely
theoretical grounds, with the magnitude of the difficulties
which oppose themselves to the successful accomplishment
of the task.'
Nor do these difficulties diminish, if the question be sub-
mitted to the test of experiment.
The valuable constituents of sewage are like the gold in the
sand of the Rhine ; its aggregate value must be immense, but
no company has yet succeeded in raising the treasure.
The character of the sewage of different towns varies with
the industrial pursuits in those towns; in towns, however,
where no special trades exist, the sewage is of a uniform
character.
The limits of this chapter merely permit of a brief allusion
to some of the processes which have been proposed.
The schemes for defecating sewage are based on pre-
cipitating the solid constituents. The object of precipitation
is to remove in a solid, dry, or semi-dry state the putrescible
constituents of the sewage, and to render the filtrate or effluent
T %
276 Disposal of
water sufficiently pure to mingle with streams, or to be
employed for purposes of irrigation.
There are two points connected with the effluent from
precipitation processes which ought to be borne in mind. In
the first place an alkaline effluent must be avoided, because
wherever there is an alkalinity there is a tendency to putre-
faction. Where the effluent can be kept acid it is safe. Another
point, urged many years ago by Professor Heisch, is that
there must not be phosphoric acid in the effluent, or there
will be a tendency to produce the low conifervoid growth
commonly called sewage fungus. That is a difficulty with
any process which employs phosphates.
The lime process is the simplest, and was the first to attain
prominence. It consists of mixing cream of lime with sewage
in the proportion of about sixteen grains of lime to the gallon.
The mixture is then allowed to subside, and the clear water
flows off. With recent sewage, and on a small scale, the
deodorisation is tolerably complete, but it leaves in the effluent
water at least four-fifths of the soluble organic matter of
the sewage. A mixture of lime and sulphate of alumina is
capable of removing a larger quantity of matter from sewage
than lime alone, and much more quickly. This process not
only removes the whole of the suspended matter, but also a
considerable quantity of dissolved matter, both mineral and
organic ; while with the lime process a minute quantity even
of suspended mineral matter is left unremoved.
The ABC process consists of using alum, blood, clay, and
charcoal. The clay and charcoal, and where necessary a
little lime, are finely ground up with water to form an
emulsion, and mixed with the sewage ; a solution of sulphate
of alumina is then added.
The sewage being a slightly alkaline liquid charged with
nitrogenous organic matter, the sulphate of alumina is decom-
posed ; the alumina is separated in a flocculent state, and, by
virtue of its affinity for dissolved organic matter, when it sinks
Water-carried Sewage. 277
it drags down with it a corresponding amount of nitrogenous
impurity : the blood is a liquid charged with albumen ; albu-
men is coagulated in the presence of alum, and in the same
way as this coagulability of albumen is utilised in fining wine
and coffee, so it is made use of in this process to join with
the alumina in its precipitation, and to assist in the further
removal of the putrescible constituents out of the solution.
The immediate action of the sulphate of alumina depends
on the presence of natural alkali in the sewage produced
by the decomposition of the urea into carbonate of ammonia ;
but a great deal of the sulphate of alumina is sometimes
wasted because the sewage is not sufficiently alkaline to
precipitate the whole of it : when this is the case lime must
be added.
The effluent water is stated to be sufficiently purified for
admission into a running stream without being a nuisance or
injurious to public health ; but the question remains as to
how far the cost of the process can be covered by the value
of the residuum.
The phosphate of alumina process consists of employing
prepared phosphates, the action of which is to curdle, and
separate the fcecal matter in the sewage, and to add lime to
separate the soluble phosphates. The solid matter is col-
lected in precipitation tanks. The effluent is said to be
sufficiently pure for admission into a river of the purity of
the lower part of the Thames, where the water is not used
for drinking purposes.
The system of the General Sewage and Manure Company,
or sulphate of alumina process, is first to pass the sewage
through strainers, the solid matter thus retained is applied
directly as manure ; the strained sewage is mixed with a solu-
tion of sulphate of alumina ; after which it receives an addition
of cream of lime, the mixture being thoroughly agitated after
the addition of each chemical.
It is then passed into precipitation tanks, of which it passes
278 Disposal of
through three in succession. The effluent water flows in a
thin sheet from the surface to filtering beds, from which it
percolates through a depth of five feet of earth and then
passes into the river in a clear bright condition.
The filter beds are used intermittently and are planted with
osiers and rye grass.
The sludge or deposit recovered from the precipitating
tanks has to be dried.
In all the systems of precipitation a large portion of the
fertilising matter passes off in the effluent water, and the dis-
posal of the sludge is a great difficulty. In proportion as the
quantity of the precipitating material is increased, the value of
the sludge or manure is diminished. It must be dried, and
unless heat is applied, the space required for its stowage
would be enormous. General Scott proposed to utilise the
organic matter in the sludge as fuel, and to produce lime com-
pounds to be used as cement, or for agricultural purposes.
He adds to the sewage a sufficient quantity of slaked lime to
produce a complete precipitation of the acids present in
sewage, and enough clay to form, with the silica and alumina
already present in the sewer water, about 20 per cent, of the
bulk of the calcined sewage sludge. When the sludge is dry
it is introduced into a kiln with a small quantity of fuel to
commence the combustion, the organic matter in the sludge
furnishes the rest of the fuel required. A million gallons
of ordinary town sewage treated with i^ tons of slaked lime
yield % tons of Portland cement.
This brief account of a few of the methods which have been
adopted for clarifying sewage, sufficiently illustrate this branch
of the subject.
Dr. Frankland states that of all the processes which have
been proposed for the purification of sewage, there is not one
which is sufficiently effective for rendering the water which
has been contaminated fit for domestic purposes. But all
these processes more or less purify the sewage, and render it
Water-carried Sewage. 279
more or less fit for turning into a river, or for further puri-
fication by application to land.
There is one way, and one way only, in which the fertilising
matter in sewage can be effectually removed and utilised, and
by which the effluent water can be rendered sufficiently pure
to pass into streams.
That method is by passing the fresh crude sewage through
the soil by irrigation in thin films, under proper and favour-
able conditions of land covered with growing crops. The soil
acts mechanically as a filter, whilst the oxidising action of
the air in the soil, and the growth of vegetation on the surface
decomposes and assimilates the organic and other compounds
in the sewage which may be available as fertilising ingredients.
By this means the trouble, nuisance and cost of precipitating,
screening and filtering are avoided, and the whole of the
fresh sewage, sludge and fluid, is incorporated with the land.
When the amount of land available is not sufficient to allow of
this being done, then concentrated land filtration, combined
possibly with some one of the best forms of chemical treatment
would have to be resorted to.
The difficulty of sewage irrigation lies in the impossibility
of always securing the necessary favourable conditions.
The best land for a sewage-farm would have a free loamy
soil, and open subsoil, with a sufficient proportion of clay to
moderate the percolative powers of its other constituents ; the
surface tolerably even, having a southern aspect, and gently
sloping to the south.
Where clay soils must be resorted to, the drains must be
frequent, in order to overcome the natural retentiveness of the
land ; and they should be so laid out as to allow the sewage
if possible to be applied twice — that is to say, the underdrains
of the land to which the sewage is first applied should dis-
charge their effluent upon a lower surface of land, by which
any impurity retained after the first application may be re-
moved by the second.
28o Disposal of
Clay land requires deep draining, and the surface should
be well broken up, either by spade labour or by deep steam-
ploughing. The surface should be deeply and perfectly
trenched, so as to secure that disintegration of the soil which
will prevent its cracking, and give it a uniform filtering power ;
the drains must be so laid and protected as to remove subsoil-
water, after filtration through the soil ; they should not allow
either unfiltered surface-water or sewage to pass through
cracks direct to the drains.
Clay soil, properly subsoiled and underdrained, would pro-
duce better crops than light sandy soils. The reason is
simple. In clay soils there are found in great abundance all
those mineral matters which plants take up as food ; whereas,
there is a deficiency of mineral plant food in light soils, and
the excess of nitrogenous matters in sewage produces over
luxuriance of growth in the plants grown on light sandy soils.
In clay soils the excess of mineral matters counterbalances the
excess of nitrogenous compounds in sewage, and more healthy
and heavier crops can be obtained, by means of sewage irriga-
tion, on well drained and well worked clay soils than on light
sandy soils.
Under-drainage and surface preparation are necessary, the
one to prevent wetness and the other to secure an even distri-
bution of the sewage over the surface, and each must be regu-
lated by the character of the soil.
Drainage can never do harm, while if the subsoil partakes
of a retentive character drainage is indispensable. In soils
comparatively free in character but few drains are required.
The inclination which it is necessary to give to the surface
of land prepared for irrigation will entirely depend upon the
character of the soil and subsoil. The area of a sewage farm
must be laid out in slopes, regulated in size and position by
the configuration of the surface and the degree of porosity the
soil possesses. With very free soils, a gradient of i in %^^ or
as much as i in ao, may be necessary to gain an overflow
Water-carried Sewage, 281
which will cover the surface and prevent excessive absorption,
whilst on very suitable soils a flat slope of i in 150 may be
a workable gradient ; the sewage-carriers should be shallow
trenches carried along the ridge nearly level, and made to
overflow evenly over the surface by damming up at intervals.
Whenever their position is likely to be permanent, they should
be made of bricks, stone, or concrete.
Every area, however rough or uneven, may have level
contour lines set out over its entire surface, so that by forming
conduits on these contour lines the surface may be irrigated.
Land having an irregular and steeply sloping surface may
have sewage-intercepting drains and carriers so arranged as to
intercept the sewage from the upper areas and bring it over
the lower areas a second or a third time, by such means more
eff"ectually purifying the sewage.
Roads over a sewage farm should, where practicable, be along
the fences ;. costly permanent roads are not required. When
land has been properly prepared for the reception of sewage,
it may be irrigated in all weathers, so as to purify the sewage.
A wet season does not necessarily injure a sewage farm if
the means of removing and consuming the produce are equal
to the growth of the crops.
One gallon of sewage weighs 10 lbs.; %%^ gallons, or 3^240
lbs. are one ton ; 22,400 gallons, or 224,000 lbs. are 100 tons
— equal to nearly one inch in depth over one acre of land.
A dressing of liquid sewage half an inch deep amounts to
nearly 50 tons per acre, a quantity more than sufficient to
fertilise any growing crop.
Ten inches equals 1000 tons, and 12,000 tons per acre per
annum equals 120 inches in depth, and this volume may be
used on well-prepared land without swamping it, as land will
filter several inches in depth per day when the sewage is
equally and evenly distributed. Looked at from a productive
point of view, this is a wasteful application of sewage, but it
answers as a means of purification.
282 Disposal of
Italian rye grass will dispose of a larger quantity of sewage
than almost any crop, and give heavy crops if the roots are
young. The greatest producing power will be in the first
year's growth. A second year is probably the utmost length
of time it should be in the ground.
No larger area of Italian rye grass should be sown than
will admit of the grass upon it being disposed of in the
district, as it will not keep, nor will it bear distant carriage.
Sewage-grown grass will however make good and wholesome
hay if the season will permit, or if the grass can be artificially
dried.
To give a sewage farm the chance of paying, the land must
be obtained at a reasonable price, and the cost of preparation
must be moderate; there must also be reasonable skill in
cropping, in cultivation, and in management; under such
conditions land irrigated with sewage ought to pay a reason-
able rent. If steam power has to be used for pumping the
sewage, this of course must be paid for in addition.
Sewage has been valued as a manure at from \d. to id, per
ton. The same sewage will, however, be worth 2d, in a dry
summer, which may not be worth even a halfpenny to the
farmer in a wet season and through the winter.
In estimating the quantity of land to be allotted to a sewage
farm it would be advisable as a rule to take one acre for 100
persons.
The sewage has to be applied carefully, so as not to injure the
growing plants ; it cannot be continually applied, as the matter
in suspension has a tendency to choke the pores of the soil.
It must be stored somewhere, to be applied at proper times ;
and when not applied at once the suspended matter should
be, as far as possible, removed. Moreover, it should not be
applied in proximity to dwellings.
These limitations have led to the adoption, in places where
land free from building is difficult to be obtained, to the other
system of direct application of sewage to land, viz. that of
Water-carried Sewage. 283
intermittent filtration. In this case one acre is allotted to
1000 persons.
Whilst irrigation may be described as the distribution of
the sewage without supersaturation of the land, having in view
the production of a maximum growth of vegetation, inter-
mittent filtration is the concentration of the sewage at short
intervals on as few acres of land as will absorb and cleanse it,
without excluding the production of vegetation at the same
time.
The best soil for this purpose is a finely comminuted soil,
with a great power of seizing on the fertilising substances in
the sewage. The drains should afford an effective aeration of
the soil to a depth of at least six feet. To secure this the
drains should be somewhat deeper than that — say a foot if
possible. Then under every square yard of surface there will
exist two cubic yards of aerated filtering material giving 9680
cubic yards per acre— say 10,000 yards. This arrangement
secures the best result ; and at the same time it facilitates
calculation, every cubic yard having a cleansing power vary-
ing from 4 to 1 12'4 gallons of sewage per diem. Hence it
follows that a single acre drained so that the sewage shall pass
through a thickness of six feet of aerated soil, will purify
'sewage proper' in quantities varying from a minimum of
40,000 gallons up to a maximum of 124,000 gallons.
Where the depth of drainage is reduced to less than six feet,
the superficial extent must be increased in proportion as the
depth of under-drainage is diminished, in order to secure the
necessary quantity of filtering material for purification.
This brief description conveys a general idea of the system,
which has been fully explained by Mr. Bailey Denton in his
Lectures to the Royal Engineers.
One third of the land is in use for a year at a time. The
sewage is strained, so as to remove the grosser particles ; it is
distributed uniformly by carriers over the area, and allowed to
sink through.
284 Disposal of
During the two years when the filtration is not in use the
land is cropped.
Present Aspect of the Sewage Question.
The following are the general conclusions to which a con-
sideration of the several methods of disposing of sewage
leads : —
1. No one system of sewage disposal could be adopted
universally: the peculiarities of different localities require
different methods.
2. With dry systems, where collection at short intervals is
properly carried out, the result, as regards health, appears to
be satisfactory.
3. It is evident that by some of the various processes, based
upon subsidence, precipitation, or filtration, a sufficiently puri-
fied effluent can be produced for discharge, without injurious
result, into water-courses and rivers, provided they are of
sufficient magnitude to effect a considerable dilution ; and
that in the case of many towns, where land is not readily
obtained at a moderate price, those particular processes afford
the most suitable means of disposing of water-carried sewage.
It appears, further, that the sludge in a manurial point of view
is of low and uncertain commercial value ; that the cost of its
conversion into a valuable manure will preclude the attain-
ment of any adequate return on the outlay, and even, it may
be, of the working expenses connected therewith ; that means
must therefore be found for getting rid of it without reference
to possible profit.
4. In certain localities, where land at a reasonable price can
be procured, with favourable natural gradients, with soil of a
suitable quality, and in a sufficient quantity, a sewage farm, if
properly conducted, is apparently the best method of dis-
posing of water-carried sewage. It is essential, however, to
bear in mind that a profit should not be looked for by the
Water-carried Sewage. 285
locality establishing the sewage farm, and only a moderate
profit by the farmer.
5. As a rule no profit can be derived at present from sewage
utilisation.
6. For health's sake, without consideration of commercial
profit, sewage and excreta must be got rid of at any cost.
CHAPTER XX.
CONCLUSION.
The conditions which should govern the healthy construction
of dwellings are embodied in pure air and pure water. Five
hundred years ago the population of the kingdom was only
equal to the present population of the metropolis. When the
first census was taken in 1801, the population of England and
Wales was less than 9,000,000 ; it has now reached nearly
25,000,000. We are crowded together as we were never
crowded before ; our pursuits are more sedentary, our habits
more luxurious ; houses increase in number ; land is more
valuable, the green fields more remote; our children are
reared among bricks and paving-stones; the public health
can only be maintained by special sanitary appliances and
precautions.
It has therefore become impossible in the question of health
for any one member of a community to separate his interest
from that of his neighbours. If he places his house away
from others, the air which he breathes may receive contamin-
ation from the neighbouring district ; the dirty water which
he throws away may pollute the stream from which his
neighbours draw their supply ; and when a population con-
gregates into towns, the influence of the proceedings of each
individual on his neighbour becomes strongly apparent.
Conclusion. 287
In places where many dwellings are congregated together,
the requirements for health may be classed under the heads,
first, of those that are common to the community, such as
the supply of good water, the removal of foul water, and the
removal of refuse matter; and secondly, of those which
immediately concern the individual householder, such as
the condition of his house and the circumstances of its
occupation.
But the existence of some danger to health in a house in
a town or village may be a source of danger to the houses
around. Thus it is the interest of every person in a community
of houses, that every other member of the community should
live under conditions favourable to health.
Each year, as civilisation and population increase, so do
these considerations increase in importance. So long as
preventible disease exists in this country, we must not delude
ourselves with the idea that we have done more than touch
the borders of sanitary improvement.
Laws alone can do little to remove or prevent sanitary
defects. A central department of the government may assist
in spreading through the community the knowledge of what
is necessary, and may publish practical methods of applying
that knowledge. To that extent government may usefully
interfere. But real and permanent sanitary progress can only
be obtained by the efforts of the people themselves ; by the
education of the nation in a knowledge of the laws of health ;
and by the creation of an efficient local administration en-
dowed with adequate power and responsibility.
The first step therefore towards further progress is to imbue
the owners and occupiers of houses and cottages with a know-
ledge of the laws of health : they are the laws of common
sense : simple and economical methods of applying them are
generally those found most effectual.
The health, intelligence, morality, and general wellbeing of
a community depends upon the condition of the dwellings.
288 Conclusion.
The local authorities in towns and villages may direct un-
healthy dwellings to be pulled down, but the removal of
insanitary dwellings should not be accompanied by over-
crowding in other dwellings. When therefore in such cases
private enterprise fails to supply new houses, it should be the
duty of the local authorities to build healthy dwellings out
of the rates to replace the dwellings so removed.
A supply of pure drinking water within the reach of all the
inhabitants should be provided ; as well as such a degree of
drainage as the local conditions show to be necessary for
ensuring that all fouled water would be removed rapidly, and
not be allowed to stagnate in ditches or on the surface, nor to
pass into streams until it has been clarified by passing over
land or otherwise.
All refuse should be rapidly removed from the immediate
vicinity of dwellings.
The plans of all new dwellings and important alterations of
existing dwellings over the whole country should be subject
to a general Building Act containing provisions based on the
principles suggested in this volume, to be enforced by the
local authorities ; and whenever the local medical officer has
reason to suspect that a cause of disease exists in any house
in a town or village, there should be a power to enter and
inspect the premises, and to require the removal, at the
expense of the owner or occupier, of any cause of disease
found to exist. Such arrangements would require that all
congregations of houses in the country districts should be
subjected to the jurisdiction of a local surveyor, such as is the
case generally in towns.
It is the function of the sanitary engineer or local surveyor
to adopt measures to prevent or to remove those sources of
danger to health which the medical officer is called upon to
detect.
The community does not permit any man to practise
medicine without having satisfied a careful and responsible
Conctusidfu 289
board of examiners that he has educated himself for his
position : and education Jn the principles of sanitary science
is just as necessary to ensure the efficient fulfilment of the
duties of a sanitary engineer or local surveyor, as is the study
of medicine to the medical man. Sanitary science is somewhat
new, it rests on the attentive observation of facts ; its true
principles have been slowly and painfully collected during
a long period, from a careful observation of human disease
and misery, by those who have preferred the study of facts to
the more enticing but more fallacious creation of theories ;
hence sanitary science is built up from details ; wherever the
details have been carefully and intelligently applied success
has invariably followed their application. When the public
realise that the progress of the nation in healthiness is to be
attained by a careful attention to these details, they will insist
that the local surveyor and sanitary engineer shall have a
complete education in the science of the healthy construction
of buildings, and in the arrangements for health to be adopted
in towns and villages ; that is to say, in the conditions neces-
sary for the prevention of disease ; just as at the present time
they require education in those who minister to the cure of
disease.
The various processes which are necessarily incidental to
life, -especially to life in crowded communities, contribute
largely to that deterioration of air and water which is a
principal cause of preventible disease. But the operation of
a free atmosphere and of running streams, provides a ready
means of purifying the air and water thus contaminated.
The evils which have arisen from this deterioration have
been gigantic, in consequence of the apathy of the community :
an apathy which results from an ignorance of the cause of
these evils, and of the means of remedying them. But the
remedy for these evils would be comparatively easy if each
member of the community were induced to perform his part in
their prevention or removal. In order to attain this end, every
U
290 ConcluHon.
member of the community should be taught the principles of
sanitary knowledge. When this has been done, and when the
co-operation of every individual in a community has been
enlisted to aid in enforcing attention to sanitary details, we
may hope for practical progress in the diminution of preven-
tible disease, and for a general improvement in the health, and
therefore in the happiness, as well as in the wealth producing
powerj of the community.
INDEX.
A.
Ablution rooms in barracks, p. 164.
— in hospitals, 165.
ventilation of, 166.
Absorption of gases by water, 198, aaa.
— of neat by different bodies, loa.
Aeration of soil, 15.
Air, circulation of round buildings, 31.
by means of open fireplace, 122,
— composition of, 37, 95.
— condition of indoors, 43-55.
— density of, 63.
— dilation and compression of, 62, 98.
— expansion of, 97.
— Alters, 82.
— flues, importance of cleansing. 1 29.
— London, impurities in, 43.
— movement of, 44, 62, 64.
— organic matter in, 39.
— permeability of materials to, 17, 1 93.
— propulsion of, 7a.
— sources whence taken, 55, 80.
— space between ceiling and roof, 193.
— space under basement floors, 191*
— suspended matters in, 38.
— warmed ; capacity for moisture, 118.
— weight of, dry, 63, 95.
— — saturated with moisture, 63, 96,
Anemometer, 67, 68.
Areas to basements, 18, 157.
Arsenic in wall paper and paint, 189.
Artesian well, 214.
Artificial lighting, 171.
Asylums, building arrangements, 160.
B.
Barracks, ablution rooms in, 164.
— arrangement of, 56, 160, 163.
— fireplaces in, 124, 133, 163.
— height of rooms in, 163.
— unit of construction for, i6a.
— windows in, i6a.
Barracks and hospitals, impurity of
air in, 45.
Basement, air space under floor, 191,
— purity of air in, 190,
— temperature, 190.
— areas, 18, 157.
— occupation of, undesirable, 18, 157,
159-
Baths, waste pipes from, 251,
U
Beams, ventilating, 86.
Buildings, arrangement oft 50, 1 56, 160.
— fire- proof, 156.
-^ numoer of stories in, 33, 161.
C.
Camps, densities of population in, 33.
— removal of refuse from, 328.
Candles, combustion of, ^4, 171.
Carbonic acid (CO,) in air, 37,
Carbonic oxide, formation of, in ordi-
nary grate, loi.
-^ in air heated by iron stoves, 108.
Cavalry stables, cubic space per horse,
179.
Ceilings, impervious to air, 192.
— lath and plaster, 193.
— pervious, 193.
— passage of air through, 54, 193.
Cellars, objections to, as dwellings, 18,
— ground air in, 157.
Cells in prisons, ventilation and warming
of, 152.
Cess-pits, 253.
— - for barracks, 254.
— near wells, danger of, 213.
— pollution of ground air and of water,
2i3» 253-
— ventilation of, a 54.
Chalk water, Dr. Clarke's process, 203.
Channels for admission of air, 81, 117.
— shape of, 82.
— material, 82.
— underground. 82.
Charcoal filters for sewers, 264.
Chimneys, movement of air in, 65,,! 21.
— resistance to passage of air, 66.
— smoky, 79.
— temperature in, 101.
Circulation of air in room with open
fireplace, 122.
round buildings, 31.
under basement floor, 191.
— of water in pipes for heating, 112.
Cisterns, cleansing of, 222.
— for storing water, aoo.
— waste pipes from, a44, 251.
Clarke's soap test for hardness of water,
aoa.
— process for softening chalk water, 203.
292
Index,
Climate, classification of, 4.
Coal, sulphurous acid from, 4?.
— consumption of, in open fireplace, 1 20.
Colour of water, ao6.
Combustion of fuel (coal, charcoal, coke,
wood), 100, 121.
— of oil, candles, gas, 43, 171.
Conduction, heat by, 104.
Conductivity of heat of different mate-
rials, 181.
Convalescent patients, 169.
Copings, 183.
Cottage grates, with open fire and oven,
13*.
Cowls, 76.
Cubic space, 48.
— in barrack rooms, 58.
— in hospitals, 59.
— in schools, 61.
— in workhouses, 58, 60.
D.
Decomposing matter, danger to health,
226.
Density of air, 63.
Densities of population for camps, 33.
Derby Infirmary, ventilation of, 146.
Dilatation of air, 62.
Dilation of air, cold produced by, 98.
Distribution of water in camps, 223.
Down draughts in ventilating shafts, 90.
Drainage, combined with irrigation, 26,
279.
— of stables, 175.
Drains in a dwelling, 239.
— arrangement and position of, 241.
— constructional requirements in laying,
345-
— examination of, 254.
— flushing of, 246.
— gratings to inlets to, 249.
— joints, 245, 267.
— materials, 245.
— shape, 245.
— ventilation of, 242, 264.
Drains, subsoil or land, 249, 269.
Draughts in a room, prevention of, 122.
Dry earth closets, 234.
Dry earth, midden, and pail systems for
removing refuse, 230.
Dryness of air, 81, 118.
Dwellings, arrangement on a site, 30.
— distance apart of, 159.
— height of, 159.
E.
Earth closets, 234.
Eaves, for protection to walb, 183.
Electric light in rooms, 174.
Emanations, production and removal of,
49.
Emission of heat from bodies by radia-
tion, 102.
Evaporation, 10.
Exhaust steam for heating, 113.
Expansion of gases and air, 62, 97.
— of water, 112, iq8.
Extraction of air, ^5, 142.
Extraction shafts, form of, 84.
— position and arrangement of, 83.
F.
Field^s self-acting flush-tank, 246, 270.
Filters for air, 82.
Filters, 219.
— animal charcoal for, 220.
— cleansing of, 221.
— sand for, 219.
-- sponges for, 220.
Fireplaces (open), action on ventilation,
120.
— in barracks, 163.
— circulation of air in a room with open,
122.
— consumption of coal in open, 1 20.
— General Morin's experiments with, 135.
— Herbert Hospital, 130.
— materials for, 121.
— two in a room, position of, 1 23.
Fire-proofing, T56.
Fittings for water-closets, 251.
Fletcher's anemometer, 68.
Floors, 190.
— Herbert Hospital, 192.
— hospital wards, 191, 192.
' — joints in, 191.
— warmed, 145.
— wooden, 191.
Floor space, 48.
— in barracks, 58, 163.
— hospitals, 59.
— prison cells, 61.
— schools, 61.
— workhouses, 58, 60.
Florence, water from Amo, 218.
Flow of water in hot-water pipes, no.
— in sewers (see Sewers),
Flue-pipes, heat given out by, 106.
— horizontal and vertical, 107.
— sloped, 107.
— vertical, 107.
Flues, brick and iron, 106.
Flushing drains and sewers, 246, 269.
Foul water, removal of, 226, 256.
French Legislative Chambers, warming
and ventilation of, 150,
Friction of air in a chimney or shaft,
72.
Fuel, combustion of, 100, lai.
— constituents of, 99.
— evaporative powers of, 99.
Index,
293
Fuel, heating powerof different kinds of,
98.
G.
Gas burners, ventilated, 173.
Gas, products of combustion of, 43, 171.
Gases absorbed by water, 198, 22a.
— expansion of, 97,
Gibraltar, sewers at, 260.
Glass for windows, quality of, 1 95.
Glazed roofs, 194.
Goux system for removal of refuse, 233.
Grates, materials for, 121.
— ventilating (see Ventilating fireplaces).
Ground air, 15.
Gullies to receive discharge from waste
pipes, 248.
— position of, 248.
— trapped gratings to, 248.
Hall or staircase in centre of house, 158.
Healthiness of buildings, 35.
— of site, 4.
effect of adjacent land on, 24.
Heat, absorption of, by different mate*
rials, 102.
— of different substances, 96.
— conduction and transmission, 104.
— given out by cast and wrought iron
pipes, 116.
— loss of, by walls, 184.
by windows, 196.
— produced by compression of air, 98.
— radiation of, 102.
Heating, by an open fire, 104.
— by a close stove, 104, 136, 139.
— by hot-water pipes, Perkins', 112..
Easton and Andereon's, 112.
approximate rules for, 117.
— by steam and exhaust steam, 113.
at Lockport, U.S., 114.
— by warmed air, experiments by Prof.
E. Wood, 136.
Heating power of different kinds of fuel,
98.
Heating water under pressure, 109.
Height of rooms, 158.
Herbage, effect on moisture, 13.
— effect on temperature, 8.
Herbert Hospital, floors of, 192.
— warming and ventilation of, 130, 153.
Horse troughs, 224.
Hospitals and barracks, impurity of air
in, 45.
Hospitals, ablution rooms and watex^
closets in, 165.
— building arrangements, 160.
— cubic space allowed in, 59-61.
— floors in, 191, 192.
— nurses* rooms, 164.
— staircases in, 168, 170.
— unit of construction, 164.
Hospitals, ward of!ices, i64» 165.
— wards, construction of, 164.
Hospital wards, windows in, 164.
Houses for residential purposes, 1 70*
Houses of Parliament, warming and ven-
tilation of, 141, 147.
Humidity of air, 46, 53.
Hygiene, definition of, i.
I.
Intercepting sewers, 262.
Iron pipes, action of water on, 200.
Irrigation, 25, 279.
J.
Joints in floors, 191.
L.
Latrines in temporary camps, 228.
Lead, action of water on, 200.
Lightme;, 171.
Lime-whiting roofs, 194.
M.
Manure, value of, 235, 275, 282, 284.
Materialsarid details of construction, 180.
— for fireplaces, 121.
— for floors, 190.
— for roofs, 193.
— for walls, 1 8a.
— for wall coverings, 187.
— permeability to air, 17, 54.
Metal roofs, 194.
Midden, pail, and dry earth systems for
removal of refuse, 250.
Model lodging-houses, 33.
Moisture, effect of herbage and trees on,
13.
— in air, 46, 53, 1x8.
— in soils, 14.
Mortality in towns and country districts,
30.
Moule's earth closet, 234.
Movement of air, 44, 55, 62, 64, 74.
Nitrates in water, 207.
Norton's tubes, 215.
O.
Oil, combustion of, 44, 171.
Organic matter in air, 39.
— in water, 205.
Overcrowding, effect on health, 32.
Ozone in the atmosphere, 39.
P.
Pail system for removal of refuse, 231.
Parian cement for walls, 188.
Paving of stables, 175.
Pavilions in hospitals, 164.
294
Index.
Pavilions in hospitals, distance between,
167.
— height of corridors between, 167.
— number of beds in, 168.
— number of floors of wards in, 167.
— position of, 167.
Percolation, 10-15.
Permeability of materials to air, 17, 54.
Pipes for conveyance of water, 300.
— for heating, 103.
Plaster for walls, 188.
Pneumatic system of sewage removal*
336.
Poison in wall-paper or paint, 189.
Pollution of river Seine at Paris, 209.
— of surface round Indian village, 229.
— of water in its transit from source, 214.
— ^- underground, 213.
Population, densities of, for camps, 33.
— of different districts of metropolis, 32.
— in towns and country parishes, 30.
— increase of, 286.
Porosity of different materials, 181.
Porous walls, 182.
Pressure of air and water, 72.
Prison cells, floor space, 61.
Privies, 230.
R.
Radiation of heat, 103.
Rainfall, 9, 211.
— evaporation of, 10.
— percolation from, 10.
— removal of, 357.
Rain-water, 199, 218.
— collection of, 218.
— impurities in, 199, 257.
Rain-water pipes, 200, 247.
Refuse from dwellings, 225, 226.
— from camps, 228.
— Goux system, 233.
— pail system, 331.
— privies, 230.
— receptacles for, 227, 329.
— solid 226.
Reservoirs for storing water, 204, 218.
Ridge ventilation for stables, 177.
Rivers, contamination of, 209.
— underground, 211.
River-water, 199.
Roads, 272.
Roofs,, construction of, 180.
— glass, 194.
— impervious, 192.
— materials for, 193.
— metal, 194.
— slated, 193.
— to stables, 177.
S.
Sand for filters, 219.
Sandstone, permeability to water, 212.
Sanitary science, education in, 288.
Sash windows, 196.
Schools, 160.
— unit of construction for, 163.
Sewage, A. B. C. process, 276.
^- cluiracter of, 375.
— disposal of, 373.
— farms, 360, 379, 284.
— intermittent filtration, 283.
— irrigation, 279.
— lime process, 276.
— phosphate of alumina process, 277.
— pneumatic system, 236.
— precipitation, 375.
— question, present aspect of, 284.
— removal of, 225.
— systems for clarif)dng, 274, 278.
— utilisation of, 274, 278.
— value of, as manure, 235, 275, 283, 284.
Sewer-gas in drains, 340.
— in water, 341, 344.
Sewerage works (see Seweri),
Sewers, brick, 367.
— Brussels, 366.
—catch tanks for heavy substances in, 369.
— charcoal filters for ventilation of, 364.
— flushing of, 346, 369.
— Gibraltar, 360.
— gradients for, 366.
— intercepting system of, 363.
— junctions at, 367.
— mud in, 272.
— outlets, 358.
— Paris, 371.
— protection of ends of, 364.
— provision for rainfall, 359.
— shape of, 265.
— size of, 360, 367,
— temperature, 343.
— tributary, 267.
— velocity of flow in, 358,
London, 359.
— ventilation of» 362, 264.
Sinks and water-closets, position of, 244.
Sites, healthiness of, 4, 27.
— position of, 24, 37.
Skylights, 158.
Slated roofs, 193.
Soil, aeration of, 15,
-— carbonic acid in, 16.
— conductivity of, 7.
— moisture in, 14.
— nature of, as affecting health, 30.
— variation in temperature of, 6.
— water-level in, 18.
Soil-pipes, 350.
— connection with drain, 351.
— material for, 350.
— position o^ 350.
4
i
Index,
295
Soil-pipes, size of, 350.
— ventilation of, 242, 251.
Solid refuse, removal of, 226.
Solvent power of water, 108.
Specific neat of bodies, 90.
Sponges for filters, 220.
Springs, 211.
— temperature of water in, 7.
Stables, cubic space per horse, 179.
— drainage of, 175.
— paving of, 175.
— roofs of, 177.
— ventilation of, 1 74*
— windows of, 1 77*
Staircases in hospitals, 168, 170.
— ventilation of, 80.
Steam boiler, temperature of air in chim-
ney of, lOI.
— pipes for heating (see Heating).
Storage of water, 204, 218.
Stove-pipes, amount of heat given out
by, 106.
Stoves, brick and iron, 106.
— cast and wrought iron, 108.
lining of, 109,
— close, 104, 136, 139, 140.
— supply of air to, lOO,
Strata, pervious or impervious, 211.
Subsoil contamination of water, 213.
— drains, 249, 269.
Sulphurous acid from coal, 42. ^
T.
Tanks for reception of rain-water, 218.
— ventilation of, 223.
Temperature, effect of changes of, on
movement of air in a room, 55.
— effect of herbage and trees on, 8.
-r- obtained from water by heating under
pressure, 109.
— of air, 4, 46, 81.
■— — as it leaves a coal fire, loi.
effect of propulsion on, 71.
effect on death-rate, 5.
in chimney of steam boiler, loi.
in flue pipe, 106.
in sewers, 243.
variation with altitude, 4.
latitude, 5.
local conditions, 5.
— of iron or glass roof, 194.
— of rooms, 95.
coal required to raise the, 120.
with ventilating fireplaces, 133.
•» of soil, variation due to depth, 6.
— water in springs, 7.
— of water stored under and above
ground, 221.
Tents, arrangement of, 34.
Trap, lead, dip of, 253.
Trees, effect on moisture, 13.
— — temperature, 8.
Troughs for watering horses, 224.
U.
Uniform diffusion of poison in air of
room, 50.
Unit of construction for asylumst 161.
— barracks, 162.
— hospitals, 164.
— schools, 162.
— workhouses, 161.
V.
Vegetable organic matter in water, 207.
Vegetation, effect on health, 19.
Velocity of air in a chimney, 65, loi, 121.
measurement of, 67.
— flow of water in sewers, 258.
Ventilating beams, 86.
Ventilating fireplaces, 1 24.
— advantages of, 135.
— application to existing chinmeys, 127.
— area of fresh-air channels for, 128.
— at Herbert Hospital, 130.
•— constmiption of coal in, 130.
— experiments on temperature, 133.
— heating surface, 130.
— size of, according to ventilation re-
quired, 129.
— supply of external air to air chambers,
128.
— temperature of rooms, 133.
Ventilation, action of open fireplaces on,
120.
— and warming of churches, 143.
corridors between wards in hos-
pitals, 169.
— ' — densely occupied buildings, 140.
— — Derby Infirmary (Sylvester), 146.
French Legislative Chambers
(Morin), 150.
halls for meetings, 144.
Herbert Hospital, 130, 153.
Houses of Parliament, 141, 147.
in rooms without open fireplaces,
136.
— — new opera at Paris, 147.
— — opera at Vienna, 146.
ordinary rooms, 140.
— — prisons, asylums, &c , 140, 152.
theatres, 144.
— by compressed air, 73.
— by extraction, 65, 142.
— — in rooms, 143.
position of flues, 142.
— by propulsion, 71.
in House of Conmions, 141.
— in hot climates, 141.
— of ablution rooms and water-closets
in hospitals, 166.
296
Index.
Ventilation of rooms, 49, 77, 85,
for dinners and receptions, 170.
— of sewers, 262, 264.
stables, 174.
staircases, 80.
workshops, 1 74.
— Roman plan, 145.
— through shafts, 65-76, 86, 90.
— warmed air, 117.
— without warmed air, 85.
Ventilators, Amott's, 89.
— the Hopper, 85.
— Mackinnel's, 93.
— Moore's louvred panes, 86.
— Muir's, 93.
— Sherringham*s, 87.
— Vertical tubes, 87, 88.
— Watson's, 92.
W.
Wall and window surface, proportionate
loss of heat, 197.
Wall coverings, 187.
— paper and paint, poison in, 189.
Walls, passage of air through, 54.
— and roofs of houses, construction of, 1 80.
— damp in, 182.
— enamelling, 187.
— loss of heat by, 184,
r— materials for, conductivity of beat
and porosity, 181.
— new, quantity of water in, 182.
— Parian cement for, 188,
— '- plaster for, 188.
— prevention of damp in, 183.
— thickness of, 186.
Wards for special cases, 169.
Warmed air, capacity for moisture, 118.
— supply to a room, 124.
Warming £^ir by hot water or steani
pipes, 116.
— by in-flow of warmed air, 136.
— observations on, 95.
Waste pipes, 243, 250.
Water, action on iron and lead, 200.
carried sewage (see Sewage),
— chlorides in, 207.
— cisterns for storing, 200.
closets, 239.
fittings for, 251.
pans for, 252.
position of, 244.
traps for, 252.
ventilation of, 244.
— colour as test of, 206.
— compression of, 112.
— contamination of, 209, 213.
Water, distribution of, in camps, 223.
— Dr. Clarke's process for softening, 203.
— expansion of, 198.
— filtering of, 219.
— flow of, in hot-water pipes, 110.
— gases absorbed by, 198, 222.
— hardness, Clarke's test of, 202.
— hard and soft, commercial value of,
201.
— ^hardness of, temporary and permanent,
202.
— high temperature obtained from, by
heating under pressure, 109.
— -level in soil, 18.
of different districts, 211.
— organic matter in, 205.
— pipes for conveyance of, 200.
impure gases in, 198, 222.
— pollution of, in its transit from source,
214.
— pressure of, 72.
— purity of» 198.
— quality of, 205.
— quantity to be supplied, 214.
— rain- and river-, 199, 218.
— solvent power of, 198.
— storage of, 404, 218, 221.
— subsoil contamination of, 213.
— supply, camps, 216.
Croydon, 21 2(
Florence, 218.
— — general principles of, 204.
pipes for, 206, 223.
— temperature of, in springs, 7.
-^ -traps to waste pipes, 240, 252,
'. — underground, 211.
— weight of, 198.
Weight of the air, 63, 95.
Wells, in London, 214.
— permanent,. 216.
lining of, 216.
preparation of surface round^ 2 1 7^
— in camps, 215, 216.
Well-water, purity of, 215.
Windows, barracks, 16 a.
— best form for ventilation, 196.
— double, 196. '
— French, 196.
glass, quality of, 195.
— hospitals, 164.
— loss of heat through, 196.
— rooms, store-closets, &c., 158, 194.
— stables, 177.
Window surface, 195.
Workhouses, 160.
— cubic space allowed in, 58, 60.
Workshops, ventilation of, 1 74,
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